Immense fun: Whilst I accept that Rock Band for the Wii is a watered down version of the game available on other platforms, it's still immense fun. The playability is just as strong as on the PS3. Whether you can choose a player character seems to me to be irrelevent to the overall gaming experience, though I accept downloadable tracks would have been a nice touch.
No controller issues: Now that the instrument controllers have their own input pads there's no need to have one game controller per instrument controller. The only extra game controller needed is for the mic, and since you get one of those with your shiny new Wii console there should be no issues in that department.
Lots of Bang for your Buck: The one thing that struck me as soon as I opened the box (one week ago - early June 2009) was the quality of the product. The instruments are sturdy and weighty and feel well put together. Even the mic impresses you with its solidity (if you felt so inclined you could knock someone out with it*). Obviously I haven't had them long enough to give them a proper road test but they feel good quality. Actually I was suprised how much you get for the price.
So there you have it, immense fun, no controller issues and plenty of bang for your buck. My only gripe would be that the game Rock Band should be bundled with the instrument box.
*Knocking people out with your mic, I'm sure, would invalidate your warranty. And would in any case be an extremely naughty thing to do.