I thought the first half was much better than the second. When it changed from suspenseful mystery to gory horror, I just found it unintentionally comical.
First time round I loved season 1 but gave up half way through season 2. A few years later, I decided to try again and was so glad I did. Probably my favourite show ever.
The second is probably the best. Third is nowhere near as good as the others but as long as you already know that, it's decent enough imo. Suffers by comparison, especially as it also came out in the same year as Goodfellas.