I've seen the drops. Probably around the low 20s at most. But never too low that it's that unbearable...Maybe not that low, but i've seen some videos where the frame rate went pretty shitty.
Might be some random thing, or it has been patched already, idk.
But yeah, i don't think it's too bad, at least we get it for the Wii.
+ They still have some time to fix things, we'll see how it goes.