My biggest problem with 00 is the moral stuff, but I'd rather not spark any arguments about that sort of thing, and it's a bit YMMV, so whatever.
My second biggest problem? The writers have no idea how to make characters likable. Some of them are okay: Graham is just a boss in general, Sergei and Soma were cool until the former died and the latter became a love interest for a terrible character, and Saji and Louise were generally pretty adorable if entirely irrelevant to the plot. But here's the thing: (mostly) everyone has development. Everyone has a backstory. THAT'S IT. There is a skeleton, and some of their skeletons are almost well put together: it's the lack of any real flesh, any real episodes to make me either care about the characters or to make their changes believable. They don't come off like real people: they come off like actors just going through their role. Because of this, the characters in 00 were some of the blandest, and occasionally some of the most offensive, characters I've ever seen in an anime. (Not to mention, TERRORISTS HELLO)
The plot's convoluted, silly, and dumb as hell, and doesn't explain a whole lot, instead taking the time to attempt to be "deep" with religious symbolism that serves no real purpose and isn't followed up on in any way rather than fleshing out the plot or explaining much of anything at all. Also, aliens? Really?
YMMV, but I hated a lot of 00's main gundam designs, but even if you like the designs, the action was just so... bland. I'm not sure how they messed up big lasers and explosions, but they did. I think my biggest issue was with the movie: even in the big, climactic action scenes, there was no real sense of flow or urgency: there were just a whole bunch of random lasers and random explosions, and we were supposed to think that something important was happening because of that, when it really just came off as a bunch of lasers and explosions.
I could go off on a bunch of different tangents but... if you like this show, then good for you. I don't, and I'm really not going to be recommending it to anyone who reads this. Skip this. Watch G Gundam
. That shit's the bomb, man.