I watched this movie last night on TV.
Although some of it was a little shoddy (like the ending, and the eventual fate of the two best friends) it was in general quite good.
The point a lot of people miss is that this is EXACTLY how teenage girls from that particular demographic talk and act. They're not articulate, they're pretentious, they waffle on about things they couldn't possibly understand, they're very shallow and they're deeply insecure drama queens. It was actually like being back at school again for me.
Ryan Reynolds also looks like my husband...so I found him pretty sexy (especially singing).
I agree that some of the casting would have been more appropriate if the actors were closer to their characters' ages, and that better editing would have tightened it all up, but it was a nice popcorn movie.
Think of Liv Tyler's character in "Empire Records", this is a movie about girls like that- neurotic, pressurised, rich kids.
It's not going to resonate with everyone, but some of us will actually manage to identify with the whole thing, and then it's really, really funny.