[CharlieB]

After my key eventually arrived (took over a week from registration), I got to try one on Wednesday.

Crikey, you'll get fit riding one! I found it quite hard work, and for that reason, maybe they won't encourage people to take cycling up. Also, on the example I tried, I thought the brakes were very poor, although this may be an isolated case.
There is a repair button on the stands to report damaged ones, but I didn't press it, in case the brakes weren't in fact faulty.

I don't know if the repair button immobilises the bike. If it does, I can imagine some mischievious persons coming along at closing time and pressing all the buttons on the stands just to be annoying.

That said, the column of numbers on the seat post is very useful when you want to remember how high you want it when you take out another one.

To be positive, they're great fun if you remember that they're meant to be ridden at a fairly sedate pace.