Soul-destroyingly, I got the wheel built up for Monday's commute, and the hub doesn't work in low gear :(
There are no controls so it can't be set up wrong. Very disappointing (have emailed the seller, and SA, to vent my spleen).
On the plus side, I can ride up from sea level just fine on a 72" singlespeed... it's getting me plenty of exercise!
Not sure now what I'm going to do for the two mini-tours we have planned this weekend and Easter.