All of the games that support Wii MotionPlus have you holding the Wiimote in one hand like a wand, and it works great (depending on the software, of course). But what about the games that allow you to turn the Wiimote sideways like an old school NES controller? Say, for example, "New Super Mario Bros." The game, which was developed to be approachable to gamers of all skill-levels, can be played just like an old school Mario game...but not if you have Wii MotionPlus attached.
I gotta say, I have pretty long thumbs and there's still no comfortable way to reach that 1 button. The palm of my right hand is pressed firmly on the end of the controller and I'm still nowhere near reaching the button. The end result is that you have to remove Wii MotionPlus, which requires removing the extra-large rubber protective case. And once that's gone, disaster is sure to follow (if the warning messages are to be believed).
Seems like a pretty big oversight on Nintendo's part, considering many of their games support (and even encourage) playing with the controller sideways. I'll be curious to see what sort of suggestions they have for getting around this that don't involve taking the protective covering off.