I had the bottom 2 out a few years ago. I fooking hated it and was shit scared.
It was done under local anaesthetic with sedation, they asked me just prior if I wanted them to take 2 or all 4. I said to take only what they needed to.
If I had known then what I know now, I would have let them take all 4. I remember NOTHING of the operation. The last thing I remember was the anaesthetic needle going in, can't even really remember how they administered the sedation.
But the suffering afterwards. I was totally out of action for a week. Eating Ice Cream and Soup etc. I reckon the suffering would have been no worse if I had all 4 done, so wished I had now as the 2 top ones are looking like they might need removing!!
Having said that, I have seen people before that have had all 4 removed and 2 hours later, you wouldn't have known. No suffering atall. So, it varies for everyone.