@Kyros: Watch out, you'll run out of arguments soon.
Let's look at the drums in Rockband, if i recall, Rockband drums have 2 drums, when Wii Music drumset is complete set. Which one resembles more playing real drums? As far as i know, Rockband drums are as much drums as DK Bongos. Also the Rockband drums are "mini" drums, while Wii Music drums are in real size (they can be minisized too if you like).
And the guitar, look how you play the electric guitar in Wii Music and you play it in Guitar Hero/Rockband and then tell me, which is more like playing a real guitar. Besides, Wii Music has the "high grip" in the guitar, like a real one.
I used Guitar Hero as an example, because it's the best selling franchise in music games and i'm personally somewhat familiar with it.
So far what i've seen, Wii Music looks polished. There have been put quite a lot of effort into the controls. Of course, i can't say how successful it is in the end, but so far what i've seen, Wii Music seems to be the best music game we've seen.
Oh, and what Guitar Hero (and apparently Rockband) is offering as a feedback, is "good, bad, miss".
@OkeyDokey: Well, that describes Guitar Hero pretty well. Or if you want to go strictly by the definition you gave, we don't have any "button mashers".
You can play the songs however you like in Guitar Hero and Wii Music, in Guitar Hero you get a score from your timing, without having any control over what you play, when Wii Music gives you the control, but no score.