I just didn't like how the film criticized everyone other than the main characters in the process of proving this (otherwise agreeable) point. It's a whiny, self-serving, and shallow way to go about making such comments (and most likely for the goal of finding acceptance from a "cool" audience, which is hypocritical when considering their message).
This is exactly why I can't enjoy "Lost in Translation." Anyhow, I think Little Miss Sunshine fares a little better by skewering its own main characters pretty well too (they act about as hypocritically as the society they're portrayed as living in). The only one who's completely innocent is the girl, who the other characters can't even remember to keep in the car at one point.
Anyhow, I agree it's one of the best movies of the year. Movies just don't take risks like this anymore, probably because of possibly offending or confusing people in this manner. It's an out-and-out satire, which surprised me.
And I didn't get an "It's okay to be a loser" theme at all. It's more like, sometimes when you think you're a loser, you're really not.