The pros:
- Incredible casting. I especially liked Jemaine Clement as Oliver, but they were all good. Even Amber Midthunder as Kerry, once I understood that her pouty petulance was part of the character; she had lived a sheltered life, in the most extreme sense.
- Gorgeously surreal art direction, genuinely making me wonder what was real at any given point in the story.
- Impressive effects for the handful of times that superpowers were visibly manifested. Most of the superpowers were telepathic or otherwise metaphysical (e.g., Syd's body swapping, Cary and Kerry's body sharing), and therefore could be depicted solely with editing tricks. But they occasionally cut loose with the psychokinetics, and I enjoyed it when they did.
- A nifty but still horrifying twist to explain Lenny's resurrection.
- I thought they were going to go the entire series without actually saying "Charles Xavier" so as not to screw with the licensing and/or movie canon. But they eventually did, just before the end.
The cons:
- The second season was much longer than it needed to be, considering what actually happened storywise. The monk's subplot in the first half of the season seemed particularly pointless. I understand that the monk was hiding from both sides and therefore used the Maze to obscure his trail, but they just got the information from the driver instead.
- The third season was obviously rushed and did not properly build on what happened in the second season. I understand that they had to wrap things up because they knew it was their last season, but still.
- Uneven use of music. I think I've had my fill of "alternative" covers of classic rock hits.
- Uneven use of musical numbers. The telepathic dance battle? Great. Oliver and Lenny invading Division 3? Also great. But then things went downhill…
- The limited number of interior sets made several episodes feel inappropriately claustrophobic. Some of that was offset by the art direction and editing, but there were still a lot of face-to-face talks over kaiten sushi. Ah well, at least they had a different set of sets for each season.
- I was disappointed by how they depicted "Legion" as basic-bitch schizophrenia. In the comics, David actually absorbs the powers and psyches of other beings (mutants, aliens, psychic constructs, whatever gets in his way), and all of them together form "Legion".
- I was also disappointed by how they depicted the young Charles Xavier as tentative and pacifistic. That might have made sense if his story ended with the end of the series and he lived happily ever after with his wife and uncorrupted son, but he's Charles freaking Xavier. In the the comics, he is a hardened soldier who takes what he learned in the previous war and then uses it in the next. Yes, he goes on to become a teacher and a scientist, and yes, he wants to build a better world in which humans and mutants can live together in peace, but he's not a damned fool about it. There is no way the real Charles Xavier would make a deal like that with the Shadow King. No way in hell. Yet that twisted sort of morality has been creeping into a lot of Marvel stuff over the last few years, both in print and on screen.