I'm sure I could count the baseball fans that frequent this site on one hand, and the Oakland A's fans on one finger. But my girlfriend saw this movie with me and she liked it, and she doesn't even know what a sacrifice fly is.
I thought this was a good movie. I was unsure how they would take a book that didn't really have much of a narrative to it and make it into a movie, but it was done really well. I really liked the interactions between Pitt & Hill and Pitt & Seymour Hoffman, especially the latter because that's exactly how I pictured the old school Art Howe and the new school Billy Beane going at each other. That was the best part of the movie, and good thing, since that was most of the movie. Also the parts in the scouting meetings were very good for the same reason.
My main critique is that it didn't really flow at times, mainly because it's hard to show statistics in a movie. The parts where they showed close ups of box scores or whatever were weird, but I don't know how else it could have showed the results of the new system.
It is really amazing what Billy did for the sport of baseball (and with no small credit to Bill James, who gets only a brief mention in the film). I wish there was a better way to show that yes, Billy's system did work, he did change the game, but that's hard since this isn't a typical sports movie where the team wins the championship in the end and hoists the GM on their shoulders. The focus of this movie is in the back office, not on the field.
So go see this movie if you like baseball, Brad Pitt, Aaron Sorkin, or good movies in general.