I don't know why they felt the need to do a movie, honestly. I thought the series finale wrapped things up pretty well.
You know, a strange thing about me is that I want to see series finales of programs that I never even watched. That's not to say I didn't watch Sex & the City; I did when I lived with Jenn. But still, I hadn't seen it since its first or second season and then I made a special effort to watch the series finale. WTF?