I was hugely excited about the Gates Carbon Belt drive system (Yes, I once rode one and even did a "homeless choobless" conversion for it's owner.) For a while it was all I coveted (well, almost). Smooth, quiet, all those things. It certainly has it's niche in the internal hub/singlespeed world, but as South Africa is so "derailleur bevok", I can't see much scope for it here, other than in the singlespeed/Rohloff arena.
One problem I have read about (and plenty of that) is of the belt drive clogging up and, excuse the word "derailling" the belt.
Seems like that issue may have been dealt with, see this write-up over at OldSpokes http://www.oldspokeshome.com/sneak-peak-new-belt-drive-system-gates
(and while you're there, check out the museum)
It's starting to look more like a chain.