I think I'm one of the few that hung in there through all four seasons. Season two was really bad, but three and four were pretty good; I really enjoyed the last season, although I thought the end of the season was a bit disappointing.

I just really enjoyed the "not-too-distant-future" take on technology and society that the show provided, and I was willing to accept a little ambiguity in the storyline to go along for the ride.