Alright - horror story time. But first, the basics, just like everyone else, definitely get a specialist no-scalpel guy that does a few thousand a year. I went to a place called weekend vasectomy and they did like 30 minute session all day long on Saturday, in-out done. Less painful than a cavity, and talked to the doc about his OIL moose hunt the whole time. The surgery was flawless and the end results were great.
Now for the crappy part. One of the more common side effects is a sperm granuloma, and it's usually pretty benign. When they cap and cauterize both ends of the vans def because sometimes one of them leaks and your body will wall it off with scar tissue and fluid and it'll go a way in a few weeks - usually no big deal. Day of the surgery, a little discomfort but no big deal, next couple days it went away to nothing. About 4 days later I woke up in excruciating pain. Near as we can work out I had a granuloma, but it adhered to the psoas muscle which is a major core stabilizer, so any movement had a direct path to yank on the testicles, which was horrendous.
Once we figured it out, a heavy dose of ibuprofen and movement to break up the adhesion (pretty awful pain) cleared it up, but for a couple days I was laid up. Still totally worth it, but just like everyone else has said- plan on some recovery time and don't go being stupid.