THE INFORMANT! is one of the best films I saw this year. It's driven by a fascinating character study. It's best you go into the movie knowing very little, so I won't write much more about it, other than the fact that Damon gives one of the best performances of the year. As much as I liked him in INVICTUS, he should have been nominated for this instead.
Soderbergh does a great job with a relatively low budget creating the weird universe for the film, an amalgam of the real early 90s and his fictionalized version which is styled like the 60s and 70s. He also does a great job of casting comic actors in dramatic roles, giving the whole film an air of parody without actually becoming one. I lived Marvin Hamlisch's deliberately kitschy score as well.
This is definitely worth a rental.