In reply to andymac:
Give them a go and see for yourself. It's a great concept, but I wish it worked a bit better. Half the time it works out quicker to walk than to go through the faff involved in using one.
Get an app to find docking stations. Citybikes is good and free.
I had a key when they first came out and it was the only way to use the bikes. It only worked one time in three and I spent more time on the phone to customer services than I did riding the bikes. Threw it away and use my debit card now, but the terminals are frustratingly slow and many don't work.
Check the bike carefully before you release it, as if you discover a fault and put it back, you have to wait 5 minutes before you can hire another.
The bikes are very heavy and top gear is so low that you have to spin like mad to reach a speed that's safe in traffic. This can be worrying sometimes.