Not really, the "punch flicking" was the only, unintended, exploit and it could've been easily fixed but that was it.
Even with that one I never had a problem with it, and I played UD3 online A LOT. There was 1 guy here saying he could beat anyone with that trick but honestly I never ran into a person who could exploit it effectively against me.
There were not other exploits, some people were complaining about side control but they just didn't know how to get out of it because they sucked (block+minor transition).
Ground game in UD3 was very very good.