I've only watched some of the episodes from Season 1, but I could tell it was really good. Just didn't have the time to follow it regularly so I didn't follow it at all.
I'm not saying that Season 3 can't be good, but I really hate it when those money hungry Hollywood execs just do whatever they want with shows. Adding more episodes on the fly (Prison Break Season 1), dragging shows on for unnecessary long (probably any US show that's passed season 4) and, the thing that I hate the most, cancelling shows in the middle of a season. A few years ago I was following this kinda promising Ocean's Eleven type crime show only to find after 5 episodes that the studio pulled the plug and the rest of the season that was already finished never aired anywhere.
Not to mention the epicness that was Joey. Luckily some Norwegian channel bought the unaired episodes so I could gain closure. Of course when a show you really liked ends it leaves you wanting more, but it's always better to quit while on top, and it seems like the British understand that a lot better.