How do I learn Linux

For one who has never touched Linux, how do you learn and how long does it take to become comfortable?

>>12
(Then it still doesn't work well because there are also Quake 1 2 and 4, Doom 1 2 and 3, Unreal Tournament 1, 2003, 2004, Neverwinter Nights, Tribes 2, Alpha Centauri, RTCW... the list goes on.)