ive used UHMW for a few months now (4-5), i am on the air bumps a Lot, and have bombed it a whole lot...it hasnt even been gouged or marked up at all, just no dirt where they contact.
it wasnt expensive...i think i bought a 4x9 rod from mcmaster (to cut in half) for something like 20-30 bucks (had to turn it down on a lathe though, get 3.5 or something)