I was on my ride today and started seeing Citibikes being used around town. One guy on one came zipping past me like he was on a road bike. I had a hard time catching him. Of course, I was 70 miles into my ride and he had just hopped on.
He said they weren't bad for riding, better than the one he had ridden in Copenhagen, where I've tried it too. Those were just ponderously heavy and you couldn't get them moving.