I cracked the Sturmey-Archer hub I had on my XtraLite in half recently and have replaced it with a NuVinci. I believe I simply subjected the S-A to too much weight and torque, and poor thing just gave up the ghost.
I picked it up today, tomorrow I'll bring my camera home and post some pics of it.

I've only put about 10 miles on the new hub, but my first impressions are:
1. It's huge (hold your hands as far from one another as you can)
2. It's the smoothest hub I've ever ridden.

It looks like it's about 5-6 inches across. Mine is silver and not black like the one in the pic above.
To "shift" it one just turns the shift knob until it reaches the torque you want, it's glass smooth and silent. On flats you can shift it while pedaling, but up hills you have to back off the pressure on the pedals. There are two cables coming from the shifter leading to the hub; Rohloffs also use a two cable system, one to pull the hub to the bottom end and one to pull the hub to the tall end of its range.
One thing that I'll find irritating is the shifter is backward to the one on my commuter (clockwise to shift up vs. counter clockwise) just something that will take a few days to change habits.

So far I think I'm going to be very happy with it, and being so much larger than my S-A it at least makes me feel like it'll hold up better.

Again, I'll post some images of it tomorrow and will post my impressions again in a week or so when I've racked some miles on it.
I'll also know if it has an effect on the battery range of the XtraLite.