I had it done when I was 20 (I'm 27 now) and I'll probably have to have it done again at some point (I'm hoping not for a few years though.) I was in a "twilight" sleep for it so I don't remember the actual procedure. Afterwards I don't really recall being in much pain. It just annoyed me having those bandage things on (or whatever they are called.) When it was taken off, I was horrified at what my new gums looked like. I compared it to raw ground beef. Luckily, it eventually looked normal (but has started to recede again.)
The only thing I really remember hating was worrying about getting food stuck around the area while it was healing. It was kind of a hassle.