My least favorite thing?
The amount of work it takes to beat
The annoying announcer that slows things down
The constant copying of all your pokemon
The music that plays the same thing OVER AND OVER
(and i like pokemon music,usually)
The slowness of the lady at the desk
The low amount of battle points you receive
The move-spamming uber kids on WI-FI
The amount of times you have to beat a leader to get the suit
The over-dramatic fainting
And... I think that's it. I like the 3D effects, though.