Yes, I realise I'm two years behind, but I just finished watching it and I thought I'd give my opinions. I'll still be as spoiler-free as possible since there must be people slower than me...right?
So upon starting to watch it, I was already aware that it wasn't going to be as cutesy as the anime I usually watch, although it stars off reasonably cute. But as soon as the first witch comes along, shit gets real. THOSE LABYRINTHS REALLY SCARE ME OKAY.
Kyubey freaks me out a bit too, always has even before I watched it. Although it annoys me that so many people assume that Kyubey must be evil or something - it's clearly just indifferent!
The first half of the series was interesting, but it was the second half that really pulled me in. I'd felt a little woozy in places, but it was episode 8 that made me super shaky even though I should have seen that plot twist coming (I read something on Tumblr that had alluded to it before, but I'd forgotten all about it until it happened). I also thought I was finally going to make it through an anime without crying, but I blubbed pretty much the whole way through the Homura episode!
I'm a little unsure about the ending. I'm not really sure if it's a happy ending or not? I guess it is, but hmmm a bit of an odd one. But then most anime have unsatisfying conclusions, and it certainly wasn't the worst!
I'll definitely watch it again, and if you haven't watched it I recommend that you do. The character development is really good for such a short anime, and the story is quite clever. I definitely intend to watch the movies (even though they are supposedly re-hashes of the series) and read the manga spin-offs once my dissertation is done!
Now I just have the problem of choosing which soul gem I should buy! As I really want one now. But my favourite character is Homura but purple wouldn't match anything I have. I'd be better off with Madoka's pink or Kyoko's red, but still I can't decide (^_^')