I have been using my MTB since the threading to the adjusting cone for the bottom bracket broke off from my hybrid. Going through alleys, deep snow, and uneven terrain is pretty great. Once you get on a smooth road again its gets slow and the knobbie tires make noise. The straight handle bar is not as comfortable as the crescent shaped bar I'm used to on the hybrid. This is definitely my last MTB of any kind.

I think its mostly the younger college age or younger crowd that rides around on the MTBs for commuting, everyone else I see uses a road bike of some sort or the occasional Cruiser.