MMB- it's do able on a single speed, but you will need a couple of cyclocross dismounts and sprint up a couple of the switchbacks. On the plus side, I can run up with a bike on my shoulder faster than gearie boys can pedal it.
If you are running a funny wheel size it can get a wee bit tight on some of the berms and the outside edge of corners that you would normally use are all feckered and crumbling away.
It's jolly good fun though.
I'll have to give it a go on a boingly geared bike, but I get the feeling it will make a lot less "interesting".