I haven't watched the last few episodes yet.
Some complaints, though:
For one thing, what ever happened to that girl Caitlin??? At some point will there be a scene like:
The front door of Peter's hotel room gets kicked down.
"Peter ye bastard, where's me sister?!?"
"The one who's not around t'stop me from cavin' in yer face! It's been months and I haven't seen you two! We feared the worst! Then I saw a replay of a clip of you on TV at some press conference where yer brother got shot, and I've been racin' around tryin' t'find ye ever since! Where is she? What have ye done with her, man?!?"
"Oh yeah, her. Uh, funny thing about that... I kinda left her in an apocalyptic future and forgot about her after that."
Several seconds of dead silence pass
"Don't give me shite Peter; I'm warning yeh, I'm dead serious!"
"So am I."
Another several seconds of dead silence pass
"WELL THEN FER THE EVERLASTIN' LOVE OF MARY GET HER BACK YE STUPID WANKER!"
"Well, you see, the problem is me and my buddies kinda caused that future not to exist."
"Bloody hell, are ye sayin' ye KILLED her?"
"Well, not so much killed, as collapsed her future existence-probability state to zero. It's like, well... imagine a cat in a box, only you can't see the cat. Now, suppose you trigge-"
"YOU'RE THE ONE WHO'S HEADED FOR A BOX, YE HEARTLESS BASTARD!"
"Oh yeah? Well let's see if a super-tazering doesn't calm you down!"
Peter points his fingers at the guy menacingly, and.... absolutely nothing happens.
"Darn, that's right, I forgot: For absolutely no good reason (other than plot convenience), I can no longer store more than one power at a time. And the most recent power I took on was from this guy who's able to make these INCREDIBLE peanut butter and jelly sandwiches. I mean you haven't lived untill you try one of them. Say, are you hungr- ow hey! Ow! OW!"
Also, that period when Sylar was changing his personality every week based one or the other Petrelli acting as his caring parent... I didn't find it very convincing. For that matter, I also thought that how that potential future Syler turned out to be a moral, caring father was too much to swallow.
And the "catalyst" stuff made absolutely no sense.
In general, however, it's a fun show.
And oh yeah-- why is it that after the first season Sylar forgot about most of his powers? Ice, liquifaction, hearing... hell, he really has no excuse to forget about them, given that one of the powers he stole was perfect memory.