I CAN NOT go to bed and just go to sleep straight away. I can fall asleep straight away if I want, but I always just listen to music, read, play ds or something for about 10-30 minutes EVERY night, whether I go to bed at ten or four in the morning.
The only exception to this is when I'm extraordinarily ill, or if I have drunk too much and am completely off my face.
If I put my ipod on shuffle I can go from cannibal corpse to tangerine dream, to leona lewis, to Sunn O))) to Beethoven to David Bowie to Howard Shore to Lady Gaga to Napalm Death and not even bat an eyelid.