"Assuming that you have a car in the States, at least you know how to drive already."
Heh, Heh. Only about 10% of drivers here in California do. Germans tend to drive better.
"If you already have hotel reservations, you probably didn't think to get a hotel with walking distance of the train stop."
Another good thing about the Bayern Ticket Lee suggests is that it's good on most buses, trams, and even some subways. If you use the bus from your poorly located hotel, buy it from the driver and it's good for the rest of your trip that day. But yeah, if you booked on some farm 6 miles out of town, it could be more problematic.
"In this country it seems you can't go anywhere without using a car. We are slaves to our automobiles."
In the US, I'd feel more like a slave if I had to ride the bus everywhere. But in Germany, public transport is vastly superior to its US counterpart. And you DO feel like a freed slave when you can travel efficiently AND your ride time is free to read, play cards, plan your activities, enjoy a sandwich and a beer, or chat face-to-face with your companion.
"I'm wondering, though, why you have only alloted one night each in Munich and Salzburg and two in Füssen? The castles aren't going to take very long to see..."
A good question. With only 4 days you are moving around, but maybe not "traveling" - getting to know these places, in other words. You're checking in, unpacking, eating, sleeping, checking out, and moving on again too quickly to soak up much in the way of experiences. Salzburg and Munich have so much to offer that 4 days is barely enough to visit those two alone. Ludwig's "castles" in Füssen are palaces, not castles, by the way; you can find palaces in Munich, and one of Ludwig's palaces in Prien on the way to Salzburg, and you can find real castles in/near Salzburg. Maybe you drop Füssen for a more rewarding trip with less ground travel? That would make transportation choices a snap.
Residenz in Munich
Nymphenburg Palace in Munich
Herrenchiemsee Palace in Prien