I don't have a mtn bike and I'm not sure I want one. Since I'm basically done with work for the winter (things are really slow these days at the bike shop), I've changed my commuter bike back to what it was before the *operation* -- a cyclocross bike. (I'm also bidding on a few cross bikes on ebay and considering getting a frame from Fort. Don't tell my wife. )
I took off the 700x28 Panaracer Pasela Tourguards and put on some cheap 700x35 cross tires. Took off the rack, bottle cages, frame pump, lights, and seat pack. I'll be hitting a few of the cyclocross practice courses and easy mtn bike trails. If I get cold, the car is less than a mile away. If I take the rode bike out and get cold, home is 10-15 miles away.