I've witnessed a few surgeries and recoveries myself, with some interesting stories.
Let's start with the open-heart surgery, where the patient was in for a triple bypass. I think the worst part of it was when the surgeon cracked and open his rib cage, that wet, cracking sound is like something out of a horror movie, and the smell from the cauterizer is not the greatest thing either (ladies, its like when your hair get caught in the dryer and burns, only a lot worse). The surgery went pretty well except the heart didn't want to start and it took a few jolts to get it working properly. I'm sure the recovery from a surgery like that is a bit painful.
I also got to observe a gall-bladder removal using the new minimally-invasive techniques where they insert a camera and instruments directly into your belly). Patient was one smooth customer, his heart rate never jumped over 80 during the prep, according to his chart he's had 5 previous stays in the OR so I guess he knew what to expect. They just take those instruments and forcebly punch them right though the belly, but I assume the recover is naturally less painful than if they actually cut it open.
I've seen the recovery in the ICU of a 600 pound man who had just completed a gastric bypass (shrunk the size of his stomach so he eats less, losses weight fast). As he woke up, he was in a tremendous amount of pain. He kept trying to pull his breathing tube out, and was acting agressive, so we had to restrain him. He broke one of the nurses hands in the process. took over half an hour and 12.5 cc's + of morphine and painkillers to get him somewhat calm. Think they ended up lashing him to the bed.
also seen people on permanent kidney dialysis, they are not happy customers. One gentleman in the ICU had stomach ulcers that burst open, and yielded a massive infection in his abdomen. Last I saw he was suffering from liver and kidney failure, with the flesh around his surgical incisions turning green, and fluid leaking from all over his body. I assume by now he is dead, or at least hope so, as that is no way to spend your last few days.