Yeah season 3 was my least favourite too i think.
Some fantastic scenes from all 5 seasons i thought. When Marlowe went to the bank in either 4 or 5... was just a fantastic scene, that did not progress the show, but emphasised his character brilliantly.
The thing was you could see every character's point of view and puts pay to alot of pre-conceptions that people (myself included) had about the material in the show.