The jacket just kills the slickness of the controller.
And, not just that, but having to take any sort of safety precaution (other than the wrist strap, which really should do just fine) kind of removes the sense of simplicity.
Honestly, how many games are so potentially hazardous with Wiimote motion that the wrist-strap isn't enough?
Having said this, I can understand why MotionPlus is going to be embedded in a glove, since games that use it will require more extreme gestures than anything we've seen before. I just wish that it was optional, as the current one already is. While I agree that the thing would serve its purpose with MotionPlus, there are some of us who still think the wrist-strap does just fine and would prefer not to use the jacket.