I love the London transit system. It's so good. I had the wonderful opportunity to visit last November and traveling by rail was great. I especially love your day pass systems that allow you free transfers between trains and busses across the entire region.
As a Torontonian, it was really funny to hear we hired one of the developers of the Underground to help us work on our subway and transit system. Their response was basically "you don't really have a subway system" so all they did was automate payment processing and quit.