This is more for my benefit than anything else, so I'll put my notes under a cut.
My thoughts are based on looking at the novels and short stories in internal chronological order (wherever it can be determined), not publication order.
Point the First: Arthur Conan Doyle's Sherlock Holmes is quite capable of being obnoxious in the BBC's Sherlock-Cumberbatchian sense. Perhaps one of the worst affronts appears in "The Boscombe Valley Mystery" (set in 1889), in which Holmes plays his "Lestrade's So Stupid That He Wouldn't Understand X" game. The example he chooses, however, 1) is one that Watson doesn't comprehend either and, more to the point, 2) is one predicated on Holmes's own knowledge of Watson's daily grooming habits gained only by the fact he's lived with Watson for years. Of course Lestrade wouldn't reach Holmes's conclusion: he's never lived with Watson, and thus he has no access to that data! The entire exercise is just an excuse for Holmes to show off, not an honest assessment of Lestrade's abilities. Holmes is none too gentle with delivering the insulting conclusion of his reasoning, for that matter, and thus he humiliates Watson. If Lestrade (or Watson) appears to get short-tempered with Holmes now and again, it's not unwarranted.
Point the Second and the More Important: Holmes shows rather compelling character development over the years (and here I'm reminded of the great man/good man point articulated by Lestrade in Sherlock), and it's instructive to watch this unfold through his relationship with Lestrade.
- In "The Five Orange Pips" (set in 1887), when Watson asks if their unknown visitor might be a friend of Holmes, Holmes replies:
"Except yourself I have none," he answered. "I do not encourage visitors."
- Yet in that same year, Holmes's professional familiarity with Lestrade leads him to treat the Inspector not as a guest who requires formal hospitality, but rather as a regular visitor free to consider himself welcome and make himself at home (in "The Adventure of the Noble Bachelor"):
"Good-afternoon, Lestrade! You will find an extra tumbler upon the sideboard, and there are cigars in the box."
- In Holmes's letter to Watson in "The Final Problem" (set in 1891), Holmes admits that he has "friends" (plural) who will feel "pain" at his loss.
- In "The Adventure of the Empty House" (set in 1894), Holmes identifies Lestrade -- in front of both Holmes's would-be murderer Colonel Sebastian Moran and, for the very first time, Lestrade himself -- as "my friend Lestrade." (He refers to Lestrade as "friend Lestrade" multiple times thereafter.)
- By "The Adventure of the Six Napoleons" (set in 1900), Holmes regularly welcomes Lestrade's social visits (above and beyond professional meetings about their joint work on a case) with a drop-by-unannounced intimacy usually reserved for one's closest friends and family.
It was no very unusual thing for Mr. Lestrade, of Scotland Yard, to look in upon us of an evening, and his visits were welcome to Sherlock Holmes, for they enabled him to keep in touch with all that was going on at the police headquarters. In return for the news which Lestrade would bring, Holmes was always ready to listen with attention to the details of any case upon which the detective was engaged, and was able occasionally, without any active interference, to give some hint or suggestion drawn from his own vast knowledge and experience.
On this particular evening, Lestrade had spoken of the weather and the newspapers. Then he had fallen silent, puffing thoughtfully at his cigar. Holmes looked keenly at him.
“Anything remarkable on hand?” he asked.
“Oh, no, Mr. Holmes–nothing very particular.”
“Then tell me about it.”
In the same story, Holmes even takes pains to consider Lestrade's personal comfort, after he's asked the Inspector to lengthen an already long day by accompanying him on a late-night expedition. Without prompting, Holmes offers food and a nap with easy familiarity: "You'll dine with us, Lestrade, and then you are welcome to the sofa until it is time for us to start."
Lestrade is practical throughout -- he bristles at insults and scorns the thought of trusting theorizing over legwork, and yet he proves willing to admit his own mistakes from the very first ("I freely confess that I was of the opinion that Stangerson was concerned in the death of Drebber. This fresh development has shown me that I was completely mistaken..." in A Study in Scarlet, set in 1881) -- but it's clear that the no-nonsense pragmatism of his relations with Holmes grows into genuine warmth and affection over time. Beyond the above examples, there are others.
- By the time of The Hound of the Baskervilles (probably set in 1888 or 1889, though possibly as late as 1899 or 1900), Holmes is requesting Lestrade's presence ("He is the best of the professionals, I think, and we may need his assistance," Holmes tells Watson), and Watson can see just how their chemistry has matured:
The London express came roaring into the station, and a small, wiry bulldog of a man had sprung from a first-class carriage. We all three shook hands, and I saw at once from the reverential way in which Lestrade gazed at my companion that he had learned a good deal since the days when they had first worked together. I could well remember the scorn which the theories of the reasoner used then to excite in the practical man.
- "The Adventure of the Norwood Builder" (set in 1894 or 1895) shows a friendly competition between Holmes and Lestrade in which each teases and mocks the other when the facts seem to fit his theory. (At one point, Holmes confesses to Watson, "...upon my soul, I believe for once the fellow is on the right track and we are on the wrong.") But Lestrade is "a practical man," as he admits, and when Holmes ultimately reveals the definitive truth with much added (and arguably unnecessary) drama, Lestrade reacts not with hurt pride or wounded ego, but genuine appreciation. (He also immediately gives credit where credit is due, telling the culprit, "You have done your best to get an innocent man hanged. If it wasn't for this gentleman here, I am not sure that you would not have succeeded.") The physical response from the normally reserved Holmes when Lestrade offers his gratitude speaks volumes:
"... I don't mind saying, in the presence of Dr. Watson, that this is the brightest thing that you have done yet, though it is a mystery to me how you did it. You have saved an innocent man's life, and you have prevented a very grave scandal, which would have ruined my reputation in the Force."
Holmes smiled, and clapped Lestrade upon the shoulder.
- And then of course there's the justifiably famous exchange in "The Adventure of the Six Napoleons" (set in 1900):
“Well,” said Lestrade, “I’ve seen you handle a good many cases, Mr. Holmes, but I don’t know that I ever knew a more workmanlike one than that. We’re not jealous of you at Scotland Yard. No, sir, we are very proud of you, and if you come down to-morrow, there’s not a man, from the oldest inspector to the youngest constable, who wouldn’t be glad to shake you by the hand.”
“Thank you!” said Holmes. “Thank you!” and as he turned away, it seemed to me that he was more nearly moved by the softer human emotions than I had ever seen him.
- Note: It's no wonder why Holmes might rely on the tenacious Inspector (in addition to his always-worthy Watson) in a situation that has the potential for real danger, such as in The Hound of the Baskervilles. After all, Lestrade proves time and again willing to confront the villains by himself without backup, including Joseph Stangerson in A Study in Scarlet and James Browner in "The Adventure of the Cardboard Box."
For that matter, although he's the slightest man physically in a room of five, Lestrade is the one to bring down the "so powerful and so fierce" Jefferson Hope by "half-strangling" him in A Study in Scarlet. Holmes underscores his trust in the Inspector by calling upon Lestrade once again in "The Adventure of the Empty House," in this case to assist in the capture of the vengeful Colonel Sebastian Moran.
Random Musings Related to ACD Canon and the BBC's Sherlock
- According to my calculations (which I'm happy to explain and be corrected upon), there was approximately a fifteen-year spread between ACD's Sherlock Holmes and Inspector Lestrade, with John Watson and Mycroft Holmes in the middle. If you take the ages of the four male leads in Sherlock, there is a fourteen-year spread between the youngest (Benedict Cumberbatch) and the eldest (Rupert Graves), with Martin Freeman and Mark Gatiss in the middle.
- Also according to my calculations, at the time of ACD's "The Adventure of the Empty House," Sherlock Holmes was 40, John Watson was 41 and nearing 42, Mycroft Holmes was 47, and Inspector Lestrade was approximately 55. As for BBC's Sherlock, at the time of the filming of the third-series episode "The Empty Hearse," this puts Martin Freeman and Mark Gatiss at the perfect ages, and Benedict Cumberbatch and Rupert Graves equally four-five years younger than their respective characters.
- I wonder if the naming of Sherlock's Molly Hooper is a nod to Molly Robertson-Kirk, a.k.a. "Lady Molly of Scotland Yard" (who was, after all, a contemporary of Sherlock Holmes).
- I suspect that Sherlock's "Greg Lestrade" wasn't originally intended to be short for "Gregory Lestrade," but rather for "Gregson Lestrade." In this way, Moffat and Gatiss could seamlessly combine Inspectors Lestrade and Gregson, who are identified by ACD's Holmes as, among the Scotland Yard professionals, "the pick of a bad lot. They are both quick and energetic, but conventional — shockingly so." (A Study in Scarlet) This theory may have been Jossed by the Steve Thompson-penned third episode of the second series (in which Lestrade is cut off as he's trying to explain that other D.I.s have consulted Sherlock besides him, and names Gregson as he's interrupted). The full implications of this throwaway mention of Gregson is as yet unclear.
 There are other interesting character changes Holmes exhibits, including his evolving thoughts on justice vs. law and means vs. ends, but I'm particularly thinking of his personal, non-Watsonian relationships at present.
 It's perhaps worth pointing out that Holmes describes Watson as "not a man with intimate friends" (save, Holmes implies, himself) in The Hound of the Baskervilles.
 Interestingly enough, Watson begins referring to Lestrade as "our old friend Lestrade" in works set in 1894 and 1895, including "The Adventure of the Norwood Builder" and "The Adventure of the Bruce-Partington Plans."