Ye gods, only one each? Okay, I'm going to reply before reading anyone else's so I don't get swept up in all the great ideas people have already posted.
Criticism: That inspiration wasn't made more integral. I *love* the concept but every single DM I've played with hasn't even treated it as "optional" but instead has ignored it completely.
Favorite: Dice modifiers and targets. To unpack, that your targets don't get too high (bounded accuracy for AC but the same idea for skills and such) and there is a easy to use and ubiquitously assigned modifier that doesn't change the result range (advantage/disadvantage).