I rated it a 6 out of 10, having just binge watched it over the past couple of days.
The visuals and audio were really fantastic, although it did go overboard at times. One moment that felt particularly over-the-top was when the dialogue turned into tiles like a silent film. Ususally the visuals and audio worked to demonstrate something specific but in that case it was just the director jerking off.
And unfortunately that was the best aspect of the show, which is a bit like saying the favorite part of your restaurant was the decorations on the wall and the music they played. Sure, that's nice, but how was the food?
I felt that the premise (there's a parasite inside a person with superpowers) was presented in a way that made it needlessly confusing and complicated. The plot also dragged on and on, with almost no movement at all. David finds out he's not crazy, it's actually a combination of having powers and a parasite in his mind. Then the parasite escapes into a new host. You could have covered that in two episodes but it takes over seven hours.
There is also nearly no character development across the season. David becomes more confidant in himself by realizing he's been held back his whole life. Everyone else is the exact same character at the end of the season as when we first meet them. There's one guy who has a change in outlook (we need to work with mutants instead of destroying them) but it's for practicality's sake, not a change in charaacter (it's just because there is a bigger threat that they need to deal with first.) There's another guy who stops secretly invading people's mind/memories but, again, it's not due to a change in character, it's just because another character tells him not to.
The acting is also generally good, except when the dialogue is bad, which gets to be more and more frequent as the series goes on. By the end of the season, it's normal for characters to be quipping quotes from songs to each other, and using analogies and anecdotes instead of asking simple questions or explaining simple ideas. Not only is this very annoying and unrealistic, it further blurs the line between the nearly-traitless ensemble cast.
One visual feature where the series almost completely failed was combat. I don't think they sold me on a single telekinetically thrown body, it always looked laughably fake. The hand to hand combat also felt totally weightless. And the "elite and dangerous" D3 had reaction times and setup strategy far worse than any stormtrooper squad in the Star Wars films. Seriously, these guys had fully automatic, long barrel guns and they constantly felt the need to get within arms reach of the good guys and, lord almighty, did these guys know how to mess up guaranteed kill shots!
Finally, by the end of the season, they made their world silly. If D3 was so set on wiping out these mutants, then really, why didn't they kill David when they had the chance? Seriously, why? The knew he could be a "world-breaker." The guy who ends up with burns all over even goes so far to say that he doesn't intend to let mutants have kids because that would cause problems in the "sandbox." So why exactly isn't D3 shooting mutants on sight or, at least, the very powerful ones?
I know that I rated this series a 6 out of 10, but as I actually look back and write out this analysis, I realize now that I was being very generous. I do not intend to watch the second season.