Its a mix of insomnia and peacefulness.
To explain the latter:
I am usually awake until around 4, 5:00 AM. The last 5 or so hours of that are pretty much silent, save for the tapping of keys and the hum of my computer. I don't know why, but I get a nice, peaceful feeling from the near silence.
Absolute silence, on the other hand, bugs the hell out of me.
EDIT:
Also, I seem to be a bit more creative at night. This is somewhat tempered by my already scattered train of though becoming a nigh incoherent string of babbling.