The Trek 8500 is a mountain bike, so I'm assuming he's asking about mountain bike tires.
I got out of mountain biking just as tubless tires were becoming easier to come by, so I only have a little experience with them. What I did ride on them I really liked. For hard packed trails I don't know that they are much better than standard tires, but for muddy situations or places where traction is hard to come by, I think they work very well.