(1) Mental skills are high up on the list. Acting comfortable in any scenario means you won't get messed with most of the time. People assume if you don't act scared/suspicious in a bad area then you are probably part of the bad area. In addition to that I learned lots of basic craftsman skills like wittling, various knot tying, and other boy scouty things.
(2) The best part is seeing a different day to day view of the world in general. It forces you to live much more in the moment. You also end up meeting some interesting people you may otherwise never be exposed to. I met a guy who claimed he was insane because the government dosed him with mercury after working on a nuclear arms project and was smart enough to back it up.
(3) Hobos come in all flavors. Some are there by choice, some are too mentally ill to function in normal society, and some are there criminally/avoiding jail.
Thanks for the prompt reply! Being a hobo sounds like a good training ground for enlightenment (kind of); especially the point of living in the moment and the ability to grow a strong mind and exude calm under pressure and stress. Good stuff!