For S1-3 Superb writing, performances. Rich, nuanced characters. Well directed, edited, shows the benefits of numerous smart creative POVs. Imo, if you can't relate to themes, characters, you might have a brain like character Amos with a very specific impairment... Humor touches very well done.
Really sweet camera work, special effects, seamlessly meshed, with rarely a discernable technical fault (ex: S3 had an episode with close shot of pool of blood; should have imo some wet with the movable; this is the low level quibble which can *very* rarely be made).
Very happy there will be a S4.
tldr: epic. Bingeable, repeatedly.