Here's my thoughts so far:
The bikes are easy to rent (when there are bikes in the rack to rent, that is) and work well as long as 10mph is your top intended speed. Bikes weigh in around 50lbs easy, but have a nice 3 spd internal hub, so you can spin as easy or as hard as you want. Having no helmet doesn't feel that great, but the lower speed helps me rationalize it a bit. In the late morning, all the bikes by the train/tube stations are gone, and end up filling up the racks at the business centers such that it can be hard to find a rack to return the bike! Same in the evening except reversed, so you had better rise early and leave work a bit early if you want a bicycle. That said, I think it a HUGE sign of success that the cycles are hitting 100% utilization in many areas of the city. Time to make the thing bigger, if you ask me. Problem is that it doesn't really pay for itself does it, and Barclay's will have to dig out their check book if they need to increase it?
Cheers!