I didn't know a lot about this movie going into it, and I was very glad that I didn't. To know a lot about this movie has the potential for spoiling the movie for the viewer, I think. So this review isn't so much of a review as a recommendation. Maybe in a few weeks or so I'll post a longer review on my Popblog.
That said, I really do recommend that you see this movie. It's clever, dark, dangerous, and highly entertaining. Identity is by far the best movie I've seen this year, and that includes seeing X2 (still the current obession, so much so that I watched Sugar and Spice today just to see James Marsden without the goggles) and Matrix Reloaded.
I definitely want to see it again, and want to drag Lou this time (went with Pat and Betsy). And Pat and I are working on making a game of this for the next TBR. That should tell you something!