After watching Vol 1 season 3 of Heroes I have to say the only good thing about it was the last episode.  The way Sylar *****ed with Claire, Angela, Noah, and Claire's mom was nice.
However, I was very frustrated with Sylar's switching loyalties.  At first when they tried to justify his evilness through the "hunger" I just rolled my eyes.  So the "hunger" made him want to blow up New York?  Yeah, that fits...

  He did lots of evil things that didn't connect to his drive for power, so it was just stupid.
However, once they started down the "redemption" road, I would have rather they stayed with that they just jump back again, because then we've literally watched hours of TV for absolutely nothing.  I think that once they had already introduced the idea that he might have a conscience, it would have been much more interesting to keep going down that road.  Have him eventually become a hero and have to deal with the fact that he has a lot of people who hate him because of all the **** he did.
Also, Arthur Petrelli just stunk of wasted potential to me.  I don't know if it was the actor who played him or the director, but the way he was portrayed was incredibly bland.  He had no charisma or presence.  When Angela told him he would release her because he still loved her deep down I was just going "really? Because I think you're off your f*&cking rocker Angela."  
I always imagined Arthur as being more like Peter, and once I relized he would be the villain, I imagined him as a Peter gone bad.  But he was just boring.  Even as a stock evil villain he was bad.  No charisma, nothing.