I've been to São Paulo many times and have always been really impressed with their metro system. It is fast, frequent, and clean. Some of their connections between lines are long and laborious, but others are simple cross platform connections. One thing that amazed me was the incredibly low dwell time at the end of the lines. The operator drives his or her train in and gets off, and then they walk to the front of the station and get on the next train that arrives. It's an elegant choreographed dance! As an operator, I don't think I would like changing trains all the time and a lack of having my stuff with me.