I have received over fifty hits this weekend from these search words--"You were right about Vesper," Bond tells M in the final moments of Quantum of Solace. I can only assume that people are trying to figure out that final, cryptic line of closure at the end of the film. And I feel bad I did not offer my interpretation of it.
I think it refers to Bond and M's conversation at the end of Casino Royale, where M tells him that Vesper gave her life to spare Bond's. This was a possibility that Bond coldly rejected then, and again in the post-title sequence of Solace.
"You were right" means that Bond has come to accepts M's view of the situation, its no long "the bitch is dead," which is another way of saying that Bond has come to terms with the pain of Vesper's loss. I think this also links up to the one truly touching point, earlier in the film, where Mathias says to Bond--"Forgive Vesper. Forgive yourself."
"You were right about Vesper" becomes Bond's way of acknowledging the pain through M, acknowledging that--as Vesper told him, just before her death, that one holds on to the past long enough to realize that they cannot forget it--without letting his own guard down.
That's my read, anyway. Maybe there was another line of dialogue in Solace that I don't remember--"I don't think the dead care about vengeance," which ties better.
Thinking about it some more, there is another possibility: M says to Bond at the end of Casino Royale that she believed Vesper made a deal with Mr. White to spares Bond's life in exchange for the money (when LeChiffre is killed but Bond is not). But Bond, in his bitter grief, is skeptical.
That revelation may be one of the things Greene told Bond right before he dumped him off in the desert at the end of Solace. That we are given nothing of what they talked about is one of the frustrating things about the end of Quantum of Solace--we are given no hooks, or juicy leads, to bring us back for the probable third film.
This leaves a huge logical hole in the franchise, however. I've always had a problem with M's opinion of Vesper's motivations in the end of Casino Royale. I always believed that QUANTUM only let Bond live then because he was the only one who knew the password to get the money back from the Swiss bank (which, ironically, turned out to be "vesper"). They couldn't kill him not because of Vesper's love, but because of his knowledge of the password which no one else knew.
Any other thoughts?