I've warmed to Mikey and Leo. But the look of Raph and Donnie really isn't doing it for me.
For Donnie, it's the glasses, when I first saw a shot of him, I thought he might be wearing night vision goggles or something cool like that, but the nerd glasses with the patch tape for some reason makes me really angry, it's a horrible and unnecessary nerdy stereotype. I've always liked that Donnie is the clever one, but he's never been so scrawny as to look like he would be beaten down by a bully for his lunch money. I'm not going with this at all. Also, his lips and nose make Mikey's first appearance seem like a real non-issue.
As for Raph, it's the full bandanna, I'm just not going with it. There's also something I don't like about his face, but I just can't quite put my finger on it.
Oh, something else. That scream from Donnie:
https://www.youtube.com/watch?v=L0-lkl9TzsU