With the new On-One Fatty coming out, I'm seriously thinking of selling my current bike and picking up a fatty. The Fatty is supposed to be trail oriented and designed with singletrack in mind, and I've seen plenty of pics of fatbikes catching some good air and doing rollers. I could also then ride year round and ride to work in the winter and just have fun in the snow. My bike has a clean 2010 AL frame with 9sp XTR derailers, LX brake levers/shifters, BB7s, and an almost new Marzocchi DJ2 fork, so I'm thinking I could get ~$500 for it. I can't afford a Fatty without selling first, so it's one or the other.
To those who have spent a reasonable amount of time on a fatbike, I'd like to hear some opinions on making a trail riding geometry fatbike your only MTB.