There are so many problems with. It is too powerful. Sylar is defenseless against it unless he gets the power where he will be too powerful. Time travel is cheap, as is freezing time. Teleporting is not too bad, though. Time Travel would be great and all, but it is too powerful. Bad for writing.

Ummmmm...in case you haven't realized this, the writer's have already addressed the over-powered time travel by having Hiro realize that there are certain things he can't and shouldn't change and having him as a morally good character who will not abuse his powers. I think the writers are doing a fine job of keeping this aspect of time travel in check.

Exactly