I've seen every season, but for me Heroes has become kind of a snore-fest. I still watch it, but, while watching, I question myself as to why I do. I really don't like many of the characters. IMO Sylar and maybe Noah Bennett are the only interesting characters.
The whole Niki/Jessica..now Tracy thing bugs me, and I really can't stand Nathan, Peter, Claire, Hiro or Matt. Nathan's motivations never make sense...Blow up NY?, Peter overacts in every scene, Claire can't get hurt...look out for her!, and Hiro & especially Matt are just 'nothing' characters' IMO.
Actually, this thread has me thinking about the show, and I'm really considering dropping it. I might be wrong, but I doubt that Heroes will be around on NBC for much longer.