I put one of these on a friend's bike. She says that it shifts fine and it was easy for me to install and set up.

But the gear range is a bit odd. Direct drive is the first gear and everything else is higher than that. So I felt the SA loses some low gears and has some really really high ones. I had to put a smaller front chainwheel on her bike, smaller than I would like with an internal gear hub. Sheldon recommends the SA 8-speed for small wheeled bikes because of the gearing options and I agree with him.

http://sheldonbrown.org/raleigh-twenty/