Not really wireless, but still better than full on wired controllers. It looks sort of like using the Classic Controller on the Wii plugged into the Wii Remote to use "wireless." It wasn't a bad setup for the Wii, but that cord was short. As already mentioned, the GameCube controller could be a problem having that lot ass cord just laying around.
Of course, the big question will be whether or not it adds lag. That will be the big deal breaker if this thing is targeted towards Smash players.