Though hitting B is awkward, its still not as awkward as shaking the damn thing. In addition, with waggle there is always some delay before the game figures out that you're waggling as to the opposed immediate response of a button press. On top of that, my older wiimote is losing its ability to waggle while all the buttons and IR still work fine. If I want to play this game with it, I've got to really go at it to get the thing to register. Luckily, I have a newer wiimote handy. But if someone else wants to play, they're screwed.
Had they followed the lead of Kart and Smash, and programmed in the classic, both the issues of using waggle or resorting to the B button could have been easily avoided. But the point is obviously moot as New Mario Bros is already "using up all of the Wii's processing power", which is why the classic configuration just couldn't fit. Maybe we'll see it added to the sequel on next years Wii HD thats coming out.