I used to have full knobbies on my mtn bike. Don't ride the mtn.bike trails now, and was looking for something for rail-trails, pavement, dirt, a tire that could handle all but full-fledged mtb trails. Currently using a Hutchinson Python 2.00 width. One of the things I like is (at least with the ones I have) is that you could run from 35psi to 80psi. On pavement, I'll run around 60psi. They do make some noise on pavement, but work well on unpaved surfaces.
