I've enjoyed this iteration, and I expect I'll enjoy the third film, but I'm happy to have it "end" there.
I LOVED Batman Begins. I agree with Nicky that it's one of those "perfect" movies. It just had, for me, a fantastic balance of elements. A Bruce Wayne I cared about, a solid origin, an interesting, compelling badguy, solid action without the action feeling like it overwhelmed the film and was an excuse for set-piece battles. Only weak part was Katie Holmes.
I liked The Dark Knight. I was irritated at how little it seemed to focus on Bruce/Batman, though. To me, that's a big part of why our sense of Bale as Batman is "GROWLY VOICE!! GRRR!!" Without the more reflective elements on Bruce/Batman's part, it's easy to slip into the sense that all you're getting of Batman himself are action moments. Meanwhile, The Joker was great but got hammy after a while (appropriate, I suppose...), and I felt that Two-Face's gradual change was interesting as a sort of parallel Batman. But the film felt...rushed to me. Not focused enough, probably because it fell victim to the "sequelitis" curse where you add too much BIG and too many characters, and lose focus as a result. That was my sense of it anyway. I've only seen it once in the theater. It's still enjoyable, just a step down from the first one.
This third one, I'm interested in it, since I've enjoyed Nolan's take on the Batman thing, but I guess...I dunno. At this point I don't NEED it to continue. I'm kinda ready for a fresh take on it, or just let it sit for a while. These franchises can wind up being pushed way too far and end up becoming bloated, so I tend to be of the "Quit while you're ahead" school of thought.