One of the reasons to fit a hub gearbox on your bike is cleanliness. A hub gearbox, properly implemented on a frame with sliding dropouts or an eccentric bottom bracket, needs no chain tensioner and can thus easily have the entire drivetrain enclosed in a full chaincase. Every hub gearbox now generally available is designed to operate cleanly -- except the Rohloff (and possibly one other which is not strictly a hub gearbox but a fully enclosed bottom bracket gearbox aimed at BMXers, but anyway not generally available). The difference is not happenstance and didn't arise from straighforward incompetence in design or execution; there are reasons.
Whereas the other hub gearboxes by Shimano, SRAM, etc, were designed for city bikes for commuters or light touring, the Rohloff was designed for offroad mountainbiking. Thus weightsaving was more important to Herr Rohloff than cleanliness, which would go unseen under layers of mud. There may have been technical reasons too why the Rohloff, unlike all the others, is not a fully sealed gearbox. Whatever the reasons, a Rohloff *deliberately*, non-accidentally, moves its mysterious ways to fulfill in an external, mostly invisible mist of oil.
You can ride a Shimano hub gearbox for years without seeing any oil, and fit a full chaincase and never see any oil from the entire drivetrain. In fact, if you do see oil, while it is remotely possible that the gearbox could be broken, the far, far greater likelihood is that you've lost the bung from the rollerbrake bolted to the gearbox! On a Rohloff-equipped bike it doesn't matter, in my experience at least, that a fully enclosed chaincase is fitted: the Rohloff gearbox will eventually 'mist' some oil onto the outside of the chaincase.
I know, to most of the fellows here, who have ridden filthy derailleurs all their lives, the amount of oil I'm talking about is picayune, totally ridiculous, just something you put up with, and adapt your wardrobe to. But I don't adapt to my property; I expect it to be my servant. In summer I wear khakis, more precisely stone-coloured chinos, all the time, including to cycle, and in seven years with Shimano hub gears never used trouser clips yet never got oil on my trousers bottoms. In less than two years with a Rohloff -- fully chaincased -- I've learned to wipe down the bike, including the outside of the chaincase, at least once a week, and have become used to marked trousers bottoms.
To summarize, a Rohloff isn't exactly a dirty gearbox, but it isn't as spotlessly clean as any of the lesser breeds either.
All I can say is, 25ml of Rohloff All Seasons Oil, a rather small bottle, goes a *very* long way, and sticks like -- er, never mind, family conference!
I'm not whining; I'm long past the vanity of spotless clothes. I realize a few spots of oil on my trousers is part of the price I pay for ultra-low gears and great strength and endurance in the gearbox on my bike. But the Rohloff's slightly oily habit is of a piece with it being more of an agricultural machine than a city slicker.
A Rohloff, for all its fine engineering, is more of a blacksmith's gearbox than a clockmaker's, that's for sure. Another recent thread is about it's character, and this is yet another reason that no one can call the Rohloff bland!
Andre Jute
The rest is magic hidden in the hub.
For rare hub gear bikes, visit Jute on Bicycles at
http://www.audio-talk.co.uk/fiultra/BICYCLE%20%26%20CYCLING.html 
