Good god this is so amazingly refreshing after basically three seasons of slogging-through and having to rage every single minute of an episode. Sylar is finally a fun villain(when he's in Matt's head at least, his how can Mohinder help, he's probably still busy with his fother's resurch in Moh's British accent, I laughed so hard) and that changes the dynamic of the show, also because the main villain now is a lot more mysterious and you're not exactly sure how he works and how far he will go, but you know that he IS evil, or at least "racist". I can't really talk about the other characters unfortunately.
Nathan, who was my favourite, is gone and Peter who I also liked has dropped the I MUST SAVE THE WORLD act and is a lot more grumpy and brooding. Hiro is still as annoying as ever but features a lot less thank god and I actually like that Claire isn't the center of the show. I was never a Claire hater but I like her current subplot. Nathan Sylar is pretty bad, but I always found Sylar (or rather, the actor) going too over-the-top when he had to play as a weak character. Noah is kinda being cast on the side to give him something of a role, although I find it funny he immediately threatened to call the Haitian when he found out Gretchen knew of Claire's power, but with Jeremy is content to just fake the deal himself.
I still find Tracy and her existence very confusing so I'm just NOT going to comment on it. Hah! Take that. The best character so far has to be the deaf woman. I find her very interesting and hey, she manages to be sarcastic in deaf-speak, which is pretty amazing! Her power is also pretty cool and she managed to make Hiro likeable, so that's a + for the writers.
Also, thinking back on it, I love how the writers just randomly write out characters. Dana Davis, the copycat was around for s2 but when Niki died she just never featured again. I don't mind(she was BORING), but that was a just an example of basic bad writing that they (generally) seem to have gotten rid of. I'm actually looking forward to finishing this season, which I haven't been able to say for any Heroes season so far and omg this became a wall of text i swear i didn't mean for this to happen.