Yeah, Hamburg's system impressed me the most of all the places I've been, even though the quality of the bikes is not great. I went to CycleHack (bike-themed hackathon) and DB gave us a bunch of StadtRad data to play around with. It turns out the Hamburg system has the highest usage in Germany by some distance, in large part because of the free 30 minutes you're given.

I think the system is still docked though, isn't it? IIRC, you don't have to physically attach your bike to a docking station when you're done, but you are required to park within a certain (small) radius of a station to end your trip.