Got this done a few years ago. The initial jabs in the baws are the worst. It was sore for a few days afterwards (like I'd been toed in the baws) but that disappeared after a few days.
Know a guy who got it done and had some horrendous problems. He was in agony as soon as the anaesthetic wore off and was given strong painkillers. This pain lasted 2 weeks and the poor guy was bed ridden. He eventually called an emergency doctor. As soon as the doc saw his sack,he called an ambulance. The ambulance came and when the guy got up to get into the ambulance, his sack and balls just fell off. Horrendous.
This never happened but hopefully it has managed to scare a few folk. It's genuinely not that bad.