I'm with you on this. While I still cling to my road bike, I put fat tires back onto one of my commuter MTBs and love riding it. The problem is there is only one set of trails here in Brooklyn, if you don't count the beat up roads (and they aren't that bad really.) I'm going to take it out for a long ride on the Old Croton Aqueduct trail in the near future.
I'll be up in Western Mass for Thanksgiving. Do you know of any trails in the Berkshires, Great Barrington area?