my impression (but I could be wrong) is that in general you can only use one of these controllers combined with as many wii controllers as you want...
while it could be impossible due to limitations in the amount of data the console can send, I think using 2 or more new controllers to play multiplayer games without splitting the tv screen (or even without turning on the tv at all) would be really amazing...
with only one of them available, it is a bit less exciting at my eyes. but I will wait until I can try it