The worst thing about Redstone Rigg is that it's a concave slope and gets steeper and steeper as you go up and up. If you find yourself in low gear right at the bottom, you find you've got nowhere left to shift and there's nothing to do but stand up and grind. Oh, and then for good measure there's 2 hairpin bends to catch you out right at the steepest section. If you stop up there, you won't get going again. Plenty of reports of people keeling over on it due to lack of speed during the Xborder100. Also, it's steep enough that walking and pushing up in "road" cleats is very difficult.
However, when you get over the top and look back, and then look at the view infront of you (weather dependent), it looks and feels bl**dy marvellous :)
For those of us that did the TrossachsTon last year, here's the crow road in comparison;
However I found this easier to do than Redstone Rigg as it gets progressively less steep so you can put it in lowest gear at the bottom and as you tire out, the lessening slope compensates.