I watched it again. And unfortunately, since I watched it alone this time, I was really nitpicky and here are some things I picked up.
I didn't realize a lot of these things at first since I was with friends - let me know whether you agree or disagree.
1. They're using a SIMILAR plotline. They need to save the world. Hiro sees the grim future. Future Peter is doing the same thing as Future Hiro in trying to fix the timeline. Why does everything seem like Season 1 again? Yes, Season 1 was successful, but seriously, think of something different. OMG, Matt is stuck in a desert (like Sylar last season). The second time I watched it, I realized it was like really bad deja-vu. I hope this season's storyline IS different, but it doesn't look like it much.

And oh yes, Claire is still having identity crisis and tries to make ANOTHER tape. SWEET.
2. There was very little character development. Why is Hiro still immature? The humour was a nice touch, but still, this is Hiro AFTER he became Kensei and watched his father die. There should have been some evidence of his personality becoming more mature and him becoming more badass. Or is Dr. HOUSE going to jump in and tell us that People never change?
3. Out of character moments? Mohinder instantly injecting himself? There was nothing in his character from the last 2 seasons to hint at such recklessness. Did shooting Bennet make him trigger happy (or in this case, syringe-happy)? He's a scientist - what happened to doing trial runs and sticking to his character. Nathan going all "reborn Christian" is weird too. It seems so sudden and since Nathan had a similar experience before, it also seems unexpected and random. And very similar to a plot device.
Yes, having it alluded that ANGELA is SYLAR'S MOM at the end was unexpected, but goddamit, how many of Heroes are actually related. Yes, we are told that these random people are somehow connected, but seriously, I thought it was them being connected by their powers and their destinies, not freaking being family members. Next thing we know, Nikki/Jessica/Tracey are children of Angela too and Matt is Daphne (speedster)'s son.
I enjoyed Sylar. And the introductions of the new villians (and their barbeque). And Bob dying. And Maya. :
Meh. I'll watch it again, but I doubt I'll enjoy it as much after picking up on all these random things.