Louise Ann and all you other Muni riders...
The only thing we could not do on a transfer was return to our starting point - as Will said, you could only make a 90 degree transfer. (Will, isn't a '180' a turn-around?)
It is only when you move out of the City that you can appreciate how well it is/was covered by the transit system. Perhaps one of the reasons is that the area is so compact. We have a pretty good system up here in the Sacramento area, but the walks are way longer to and from the bus stops, they don't run as often and there is simply no comparison to SF.
London, Glasgow & Edinburgh have good transportation systems, too - much easier than trying to drive, especially through the downtown areas - I can't speak for other cities, though.
Yes, the beer is good today!