I got the M and didn't like having the Google Search on top of every screen. I DISABLED Google Search. Then, none of my voice inputs would work. Specifically if I opened Google Navigation and hit the microphone I'd get a message that said: "unfortunately Maps has stopped". Talked with a Tech and nothing fixed the problem. I got a replacement phone and did the same thing, disabling Google Search. I went to Navigation and same error. I factory reset the phone. I left Google Search on the screen and no more voice input problems.
Hope this helps someone with this problem and keeps you from disabling the search.
Pretty sure Motorola and Google are aware of this now as they got a notification from a 2nd level tech about it.