Mixed bag to be honest. The Pilot was absolutely brilliant in terms of atmosphere and horror, but there were a few episodes that really showed the show's warts - namely some jarringly terrible dialogue and some fairly inconsistent acting performances. However, the cool parts of the show - generally above average directing, some solid developing storylines, and most of all some incredible makeup and effects - make it definitely watchable and fun. Also, early reviews for the Season Two premiere have been fantastic, so there's that.
The premier was great. The second episode was really good. Once the main character found other survivors it fell off a little bit. Still worth watching though. The first season was six episodes long, it's more worth a chance if you've got nothing to do.