Before Annie Hall, I had only seen the more recent Woody Allen movies. Vicky Cristina Barcelona (very good), Match Point (good), and Scoop (awful). Needless to say Annie Hall was a bit of a shock. It was was very different from those later Allen films.
I love how Woody is unafraid to throw any and everything at the viewer. Any story-telling device or technique that he wants to use, he just goes for it. Talking directly to the audience, flashbacks, asides, they all combine to tell the story of a relationship - piece by piece. This isn't a straightforward narrative, and it's a better movie as a result. Every time I thought things were beginning to bog down a little, some awesome joke or interesting narrative flourish would come out of nowhere and jolt my interest back into what was going on. That's how you make a relationship movie interesting for those who typically avoid these kinds of flicks.
Take all those complimentary things I've just said and wrap them in the kind of bittersweet, memorable ending that I love, and you have Annie Hall in a nutshell. I never really appreciated how smart Woody is, before i watched this. It's funny and intelligent and full of the kind of references and jokes that makes me wish I could write this kind of thing. Great movie.