huh, I didn't know they had this in IMAX format. I did see it in the regular theater though, and liked it pretty well. They managed to finally do a good translation to screen of an Alan Moore book. It sticks fairly closely to the comic but manages to cut out the stuff that was superfluous and/or a little hokey in the book. I thought Hugo Weaving did an excellent job considering he had to emote with just his voice and body language. And Natalie portman, she's just the bee's knees.
Though now thinking back on it, wasn't her character arc very similar in The Professional? hmmm...
