Yes, I've ridden a few Citi Bike bikes with the NuVinci hub. Each time I ride one, I like it more. I got one yesterday and had a lot of fun with it. The bottom ratio is insanely low, but given that we want little people to be able to ride it, I won't complain. It's hard to make a bike that pleases everyone, and they struck a good middle ground.

I believe these bikes have the N330 model which means the top ratio is 3.3 times the bottom one. There are N360 and N380 models available. There's probably not much point in using them on the bike share bikes.

I've adjusted the ratio while stopped and while pedaling. It just works. Whee!

And yes, the bikes get frequent maintenance. I've read about it. The repair depot is extremely busy. When docking a bike, you can press a button next to the wrench icon which will lock the bike, turn on a red light, and take the bike out of commission until a mechanic picks it up. Then you can give feedback in reply to an email they send you automatically.