No, I haven't seen The Dark Knight yet, but I plan to see it soon. I've no fear of spoilers, however, and I've already heard all about the boat scene. There's a fascinating discussion of it here, using game theory:
As always, readers are smarter and think harder than writers, so the comments are important to read, too. I don't know everything about Batman, so I couldn't be sure if this is something from the comic books, or if Chris Nolan came up with it himself, but either way, it's genius.