Big fan of True Detective S01 - S02. S01 was especially superb, and I feel it's WH & MM's best work.
S02 was great as well, and took a completely different approach by having the storyline follow a more traditional narrative (i.e., not going back & forth in different time periods like S01).
So far, S03 is excellent - I've seen the first three episodes. Very impressed by the acting, storyline, and haunting/brooding atmosphere. Very seamless transitions between 1980, 1990, and 2015. Elements of this storyline were obviously inspired by the infamous & heinous crimes that occurred in West Memphis, AR in the early '90's.
As in S01, the theme of older detectives remembering & being haunted by crimes they investigated earlier in their career is a very strong element here. Having the two lead detectives (Hays & Dorrf) be Vietnam veterans was interesting, especially given that Hays used his tracking skills to find the horrific crime scene. Also amused by the "Purple Hays" nick-name, which was an obvious reference to the iconic 1967 Jimi Hendrix track "Purple Haze"...a song that American troops in Vietnam would have been listening to in the late '60's & '70's:
https://www.youtube.com/watch?v=fjwWjx7Cw8I