I also saw and really liked Michael Clayton. But I have a question...
What did you think about Marty, the head of the law firm? Do you think he was a bad guy - maybe wanted Clayton and Arthur dead? There's no real indication that he is bad. In fact, there's more examples of him liking Clayton, saying how important he is to the firm, loaning him money. But something was said in that final conversation between Clayton and Karen, in which she brought up Marty, and Clayton said something like "Good, I hope you do tell Marty." And you know he was panicked when he discovered Arthur's plans, and couldn't take being sued by U-North. It just makes me wonder. I could be totally wrong, and it doesn't seem to matter to the plot really anyway.
End of spoiler.
Very solid acting, fine cinematography and very intelligent script.