I don't think American Idiot deserved all of the abuse it gets, but it's overplayed aswell. It's a good album, and has some great songs on it, but they got rid of the punk aspect of their music (They're now pop rock instead of pop punk).
The whole "guyliner" and skinny jeans thing is probably something of a marketing move, but it's up to them how they dress. I think it suites them actually, I don't think they sold out, but the message wasn't a new one, and some of the songs are pretty generic. The reason it was so well receieved was because it was Green Day, and it was an unexpected move from them.
The songs and the storyline are darker than their old albums, and even I thought the Jesus of Suburbia video was overdoing it abit (Still love it though). Compared to the frat boy humour of their older albums, it's somewhat more mature and more deeply written. It's a very lyrical album, and you can extract several meanings from the words, it's great as a collection of songs, but it's best as a chronological story.
I have to say if they had contiuned with their old pop punk style it wouldn't have been the same as Dookie,Insomniac and so on. They're all nearing 40, you can't write songs about madturbation and living in squats for ever. I don't think they have the same energy on stage as they once did, and what's the point in a pop punk song with no energy?.
Billie Joe has said that the new album (Released sometime this year) is going to be a kinda "power pop" album. Sounds interesting but I'm somewhat cautious about whether they will fully go down the "Whiny emo pop" route.