Party chat is terrible. If someone lags or someone's controller disconnects, you'll still be in the party, but can no longer communicate. You have disconnect from the party completely, and rejoin in order for it to work again. I don't even understand why it's associated with the controller disconnecting.
Also noticed this when it party chat, if the controller disconnects, or you turn "party chat off," the volume of the xbox decreases by a substantial amount. Only fix is to leave the party completely or turn party chat on.
For some reason my controller disconnects all of the time, causing me to lose party chat functionality, as well as the having to unpause the game (it sucks when playing multiplayer online). I don't know if there's interference from a nearby router in my basement, but I think it was a terrible idea to use WiFi Direct for the controllers. I wish there was a way to alter the frequencies.
These are really my only gripes.