Robbie,
I have 2 sets of wheels for my Trek 6700 mtn. bike. The first set is pair of all out trail wheels that were OEM on the bike. My second set is pair of Mavic Cross Rides with Continental Contact semi-slick tires.
The Maivc set-up is extremely fast but durable enough for a variety of single track riding. I have no traction issues with the semi-slick tires.