We have family in town right now who are staying in the south end, and this means more rides on buses and subways for our little family than usual. Yesterday we took a bus to the science museum, a train to "vacation house" (as H. calls it), and then a pair of trains back home. Since we were riding at rush hour, we took H. out of her stroller and let her ride either sitting on my lap or sitting on her own seat. She hasn't yet done much riding outside of her stroller, so we were curious to see how she would do.
The results were mixed. She was happy to be sitting in her own seat, but was a bit more vigorous that most of the other riders probably would have enjoyed. She liked looking out of the window, but sometimes had to be reminded to be quieter in her enthusiasm. She needed frequent reminders to continue sitting and was squirmy enough that the trips made me tired. During the last ride, we had to get off of the train because H. got a little hysterical when the nice man she was flirting with moved a few seats down (either to get away from her, or to give us room to sit down next to her -- I'm not sure which). We put her back into her stroller and told her if she didn't calm down we would get off the train. She didn't, so we did, and we got back on the next train with a calmer child who stayed in her stroller.
So we still have some things to work on. We want her to be safe on the train, to listen to us, and to sit in a seat (although I think we're deciding that kneeling in order to be able to look out the window is OK). We've been thinking of taking some "practice" stroller-free train trips with her for short distances so that we can work on the rules of riding in situations with less pressure.