I got this for Christmas, and have had quite a lot of fun over the last few weeks watching it. It starts out as a sci-fi epic drama series about people who discover they have superpowers and try to stop a nuclear explosion in New York while avoiding the evil super-powerful series killer Sylar. Lots of end of episode sudden twists and cliffhangers, good fun if very very dark at times - it's probably gorier than Predator, for example.
BUT... there's always the slight danger of heading off into the whole soap opera about superheroes trying to live normal lives and solve everyday problems thing. As far as I can tell from watching episodes from later series, that's where it ended up, but it's only there as a slight weakness in series 1. I tend to like superhero films and so on - usually good escapist fun, but can't be doing with soaps. There are a few episodes in series 1 which seem to be setting that sort of thing up.
So great fun, but I don't think I'd go for series 2, 3 or 4, all of which have had much lower viewing figures than series 1. The ending of series 1 is fairly unsatisfactory and doesn't really fit with the rest of the series. Here is how series 1 should have ended for a more satisfactory conclusion IMHO:
Sylar makes another attempt on Claire, but is thwarted by Mrs Petrelli (who must have some kind of superpower). Hiro (who can time travel and teleport) uses his ability to create a squad of 6 or so Hiros, who then kill Sylar without any of the Hiros dying. And they kill him properly - decapitation or something, but not before Sylar has killed Mrs Petrelli. Peter Petrelli is filled with grief and anger, and starts exploding. Meanwhile, Hiro, DL and Nathan use their and Hiro's abilities to try to evacuate people from the blast area. Claire tries to save Peter, but only succeeds in sedating him after he has already done enough damage to fulfil the paintings. The series ends with someone coming across Sylar's head, only to find it has been cut open and his brain taken.