It's not like the Wii was ever short on control pads, but hey, if Nintendo feel we need another one - in this case the Classic Controller Pro - then we're not going to argue.
There's no word yet on price, or a firm release date (just that it's coming in the Summer). The Classic Controller Pro differs from the original Classic Controller by adding some extra shoulder buttons, spacing the thumbsticks out a bit more and introducing some hand grips.
Should make playing those N64 games (and PS2 ports, looking at that layout) a damn sight easier.