I watched the entire first season yesterday and thoroughly enjoyed it. It's like 28 Days Later (the fact that Grimes wakes up in a hospital for example immediately reminded me of that movie) meets the BBC's Survivors (the location in the last episode recalled series two of Survivors). I guess it's 28 Days Later U.S.A. really and far from original but Frank Darabont's involvement gives it the same eerie atmosphere that his excellent The Mist had and this series even includes three of the cast from that movie. Fellow Brit, Andrew Lincoln, delivers a good performance (plus convincing accent!) and it was a while before I remembered he isn't American; I recognised him but couldn't place where I'd seen him before (he was in This Life). Looks very sexy in that uniform too.
It's a shame season 1 is only six episodes as it left me gagging for more (hell, I'd have been content with an extra two seeing as disc 2 seems half-full) but I've read that season 2 is only a couple of months away and will be 13 episodes. Can't wait.