I had a similarly pleasant travel experience while visiting Moscow on a whim. It was a bliss to get all around the city and back to where I was staying easily. Trains would come often and would have multiple connections (and if you missed a connection, you could just take one of the circle lines to get to the line you missed. And being from southern California, I definitely agree with your comment about how much more difficult a trip to LA would be without having access to a car.