I have one of the latest Wii models (that black one that comes with NSMBW). It unfortunately lacks GameCube controller and memory card slots so I had to settle for using a Classic Controller Pro and it's honestly a pretty solid controller.
It doesn't really take long to get used to, though I suppose that was only my case because I haven't played Melee in forever, and when I did I was still young so I didn't really play it at the fast pace we see today. I didn't really have to shift from one controller playstyle to another, I suppose.
Anyway yeah, really good controller imo. I use it all the time and I'd recommend giving it a try at least, you won't know how to really feel about it until you do I guess. The Wii U one looks really different though, so if the one for normal Wii can still be used on Wii U then people like me that are used to that one will probably stick to it. If that's the case I'm pretty sure I will.