Ok, I've finished the show. Overall, it was pretty alright. There are some weak elements, and some annoying characters (Andy got really annoying when he went full mutant supremacist mixed with teenage BS, but the major problem with the show is that the villains all suck until the Hellfire Club is introduced. The sentinel Services guy is too bland, and the show should never have tried to make him "sympathetic", because it didn't work. I don't care that his kid died, he's as much of a monster as Campbell. Once the Stepford Cuckoos, then the show had interesting villains. A quick rundown of my opinion of (most of) the characters:
The Struckers - Their family history is really interesting. I liked how the show had a point to using the name, and wasn't just doing it as an obscure Marvel Comics reference. In individual family members kept fluctuating when it came to what I felt about them, but I ended the season liking the parents and Lauren (although all three had moments where they annoyed me), and disliking Andy. He started out generic, and got really annoying when he entered his "My psychotic grandparents were actually the victims" mutant supremacist phase.
Eclipse - At first, he was just the guy who looked like Oscar Isaacs, but I'd say he's tied with Blink as my favorite Mutant Underground member. I wasn't the biggest fan of his mob stuff, but outside of that he was the MU member with the best head on his shoulders. His relationship with Polaris was good, and I'm glad he didn't just give up what he thought was right when she became a villain at the end. I wish he hadn't been an idiot about the mob stuff, but thats the worst I can say about him.
Thunderbird - As a character I liked him, but he had a tendency to do stupid crap for no other reason then the writers needed drama (something basically every recurring character did, to be fair) which held him back a bit.
Polaris - She's a good character. I liked her in general, and her relationship with eclipse was generally good. I think her last minute heel turn was a bit too quick, but it does make sense when you see what happens to her over the course of the show, and I'm sure she's going to end up finding out she fucked up really badly by choosing to join the Hellfire Club.
Blink - She had an interesting journey during the show, gaining control over her power and having her attitude change. The stuff with her backstory, and what happened to the mutant foster house, was intense. One thing I liked is that most of the drama she was involved in was her reacting in a way that made sense to screwed up situations, like when dreamer messed with her memories. It made total sense that she'd leave because of that, but it also made sense when she returned.
Dreamer - She was a background character for most of the show. She worked for what she needed to be. I didn't dislike her, but I didn't really care when she died, either.
Stepford Cuckoos - They worked well in this. They're manipulative, completely without morals, and are actually interesting as villains in the way a Brotherhood of Evil Mutants style group should be. The show also pulled off the three of them extremely well, I never saw a scene were the effect was messed up. It always looked to me like there were three of the same person on screen when there was supposed to be, and not just a camera trick.
Overall I liked the show. It had a few huge flaws (like bad villains for the first 3/4ths of the show, and a few bad episodes, like the one where the twins were being tested by Campbell), but it was entertaining and I'll watch a second season, which is more then I can say about most superhero TV shows at this point. Hopefully with everything set up in this season, season 2 will be a bit stronger.