I had mine out when I was 16- all four were severely impacted. I had friends who were awake during their surgery and were numbed. I told the oral surgeon that I didn't want to remember a thing, and so they knocked me out completely. I would not have been able to handle watching the dentist pull out my teeth, even if it didn't hurt. I knew I'd freak out.
I remember they gave me the shot and said "you can start counting backwards from 100." I said "Okaaaay... zzzz..." and the next thing I remember is the dentist handing me a plastic bag with my teeth and telling me everything is fine. It literally felt like a second had gone by between going to sleep and waking up.
I'm sure everyone is different, but I didn't feel any pain and was starving because you aren't supposed to eat before the surgery. I went home a ate a bagel. :-D Granted, my mouth did bleed a lot for a day or two, which was gross, but I didn't care- I was starving which I'm sure made things worse, but oh well. I kept rinsing my mouth out and after a day or two I was fine. I didn't even swell up or anything. It was a very easy procedure for me, but I also had a very good oral surgeon.
I had mine cut out a year and half ago. It wasnt bad at all. You go there, lay down, they put you to sleep and then you wake up. As long as you stay clean and do what they tell you for aftercare it shouldnt be too bad. my brother didnt follow what they said and he was in a lot of pain through a week or so, while I just had really bad pain on the first day.
Also, if you are not afraid of it, its kind of fun making blood drip from your mouth.
I had all four done last year. In general, once you go under it's pretty much smooth sailing from there, but I would recommend having an MP3 player with your favorite music/poetry/audiobooks/etc. if you're nervous about the going under part, so you have something to focus your mind on until it's done with.