Familiarizing file & directory structure itself might take a while. In fact I got http://www.tldp.org/guides.html from some one's signature (drag) and that helped me in getting some idea. I am yet to learn it seriously though.
I have been trying Linux on and off (almost once a year) for many years now (first one was Corel Linux in 1999/2000), but never thought of adopting if for mainstream use. It was never a requirement since I could always tame Windows however naughty it behaved and after moving to Windows XP, there was no reason to try anything else. In recent times I found Linux to be getting easier to use (upgrading, finding new application etc) and fun (may be the challenge of trying the unknown). I learned more about Linux only after started using it for my serious work. That said, all this only for my personal use. (I still use and love Windows and its development tools for my professional use).
