So we've all seen that not many people like Riven...
and though I don't have too much of a problem with her myself, I do know part of the reason.
AA'ing canceling. Seriously, if played right(though it can be hard), I'm fairly positive Riven can get 3 AA's and her 3 Q's in within 2 or 3 seconds at level 1, which is pretty OP.
But seriously, just remove or nerf her AA canceling and I think people would finally see her as at least fairly balanced. I mean, she already has a stun and knockup to make up time for AA's, why the canceling? Plus her ult extremely enhances her and is on a really low CD, especially when building CDR.