In a word, fabulous. One of the oddest, most unique experiences that one can have in their life. Having absolutely no knowledge of what happened to you other than that it did happen is stupendous. The best experience with being anaesthetized was in my dentist's office, having my wisdom teeth out. The nurse put in an IV, which was an interesting experience unto itself. Then, in a sweet voice that only someone who is totally disassociated from your current situation can muster, she says, "I'm going to give you something to relax you." Ha! The first shot of chemicals, whatever they are, make you feel amazing. Giddy and wonderful, all at once, 5 seconds after she pushes the plunger. Afterwards, she states that the real stuff is coming next and that you should start to count backwards in your head. By 80, you're unconcious. Black. You awaken to smiling faces with gauze in your mouth and the steady beep of a heart monitor in the background.

If you really like these experiences, you should probably stay very very far away from actual intravenous drugs, because you are susceptible to addiction, moreso than anyone else.