12 years ago I did the great divide on a regular mtb frame with my rohloff hub. I had no problems whatsoever.
People often rightfully claim that they dont want such a complicated gear system, because you cannot fix it on the road like a derailleur system. That is very true and I understand the problem. However, the hub is so robust that it will not fail at all ... mine did not ... and I would do it again. I have never opened and serviced the hub, and would not do so if I had to do the trip again.
Try reading this post about a guy who used both the rohloff and the belt drive.http://twentynineinches.com/2012/08/03/interview-with-tour-divide-winner-ollie-whalley/
Based on his interview alone, I transformed one of my bikes into a belt driven bike and I would like to turn my Rohloff bike into the same.
When discussing negative issues:
1. There is a bit more drag in the hub, you will probably never notice it offroad, but I am sensitive and would never do a trans am on paved roads with a rohloff, because it drags a bit more.
2. In particular gears it makes a clicking noise, so it is def not silent.