Tbh I don't begrudge Nasri leaving... it's not a crime to want to win trophies, or even want more money, really... If someone offered to double or triple your wages if you switched employers, I think everyone would take that chance.
IMO the only reason why Arsenal fans (including myself) aren't happy with Nasri, is that he started making digs in the media about Arsenal... Fair play to the guy for going to a club where he's paid more, and he's more likely to achieve success, but you should respect the club / supporters / manager that gave you their backing for the duration that he was playing for Arsenal. Just makes him seem ungrateful / undignified, really.