Yes they stand up to the rigors of mounting biking, I have three, two purchased from new and one purchased second hand.
They are literally bomb proof, first one was purchased in 2003, still going strong, has been on two or three different bikes, survived two trips abroad to Saalbach and Chatel.
Did break a couple spokes after death gripping a rock garden in Austia (fixed in 15 min back at the hotel), it has had two sets of cables and an oil seal change which I did myself with the correct rohloff tools.
They do put all the weight in one place (back wheel) but you adapt to this and the only thing better is the pinion gearbox.
Had a Nicolai GPI with a 12 speed pinion for the last 5-6 months and……….. tis a thing of wonder and delight 🙂
First time I have considered selling off the other bikes to fund a second pinion bike purchase.
There is also the very new Kindernay XIV Hub, which is supposed to be lighter than the rohloff and looks a very interesting alternative with hydraulic paddle shifter for those that don’t like grip shifters.
Love gear hubs/boxes me 🙂