I have the Pioneer pants too. Overall I like them. In my climate I usually do not use the liner, and with shorts underneath I've been comfy up to the low 70s although being black, they do heat up in the sun. I wish they had higher zippers, as they can be difficult to get boots through. I agree about the belt- in fact, the adjustment on mine pulls the top-snap open! I do not have a jacket to which the pants will zip (FirstGear Kili- no zipper in it at all), so I hold them up with a set of tool-belt suspenders. This works pretty well.
I went down in the Pioneers once. Fairly low speed, but I slid on my hip for a few feet. It barely marred them at all.