brilliant, i've ridden keystone a bit and like it a lot, rocky and rooty. I try to ride Turkey Mt twice a week when it's not muddy, closer (in city limits) and something for everybody. Fun day trip/overnight rides over in NW Arkansas to be had also.
http://www.dirtworld.com/trails/trail.asp?id=12878
http://www.okearthbike.com/trails.html
http://www.dirtworld.com/trails/trail.asp?id=12878
http://www.okearthbike.com/trails.html