The BikeMi bike share network in Milan is very extensive, easy to use and even provides confirming emails to advise you that you have successfully returned your bike.
However, I only give it an average rating because so many of the bikes we used with the service were in such poor shape and they are very heavy. There is no way to identify to the service that a bike needs maintenance, you just park it in a slot again.
Note, there is a 2 hour time limit for each individual use and extra charges for any use beyond 30 minutes.
On the plus side, the bikes have lights and a cable lock for use when stopping for a bite to eat or when shopping.