I received this bad boy for Christmas - one of the lucky ones, I know - and am loving it. My wife and I play it to death. While that may seem a hyperbole, it's not since we've killed 4 pairs of batteries for the Wiimote since Christmas. That's eight batteries dead, never to come back, and I regret nothing. The game is just that awesome.
I guess what I enjoy most from this iteration is the guitar itself. It's wireless, thanks to the Wiimote, and feels much lighter than similiar models on other consoles. The Wiimote fits in the guitar nicely. There's a cable much like the nunchuck's to connect the Wiimote to, and slot in which you press it snuggly into. Everything else looks to be the same as the other consoles - including that accursed orange button!
The song selection is respectable given this is the fourth game in the series (I know it says Three, but Rock the 80s is actually the third game), hopefully Activision will change their minds and work with Nintendo for some downloadable content later on. However, even if there is no future content for the Wii, you'll have plenty of songs to satisfy you for months to come.
Overall, this is an awesome game. The only complaints I have is limited ability to procure extra guitars (I've yet to find individual Wii guitars, as far as I know you'd have to buy another Guitar Hero III bundle), no foreseeable extra content, it's only in mono (a mistake Activision claims they will correct for free) and that orange button is still a pain to get to.