My boy Pooka didn't think it was torture as far as I can tell. XD He recovered quickly, though he had two slight complications following surgery. He messed with it and caused the incision to bleed briefly, but that healed on its own. He also developed a small mass around the site that was an abscess, which happens sometimes. I took him to the vet for it, the vet popped it and drained it, put him on antibiotics, and it was healed within two days.
If your rats have has a lot of respiratory issues, surgery is a lot higher risk as it suppresses their breathing (with anesthesia). If their breathing is already compromised, it could cause them to stop breathing. For example, my girl Cream was covered in tumors and the vet suspected they spread to her lungs. I decided putting her down was the best option as she could barely breath, but when they sedated her (so she wouldn't feel the final injection), she stopped breathing all together. However, my girl Silver suffered from URIs all her life and made it through an emergency spay. My boy Bartok also had breathing problems and he survived surgery as well. It really depends, but if your rat is in good health, the risk is lower. I do know of one person who used to be on this forum that got a very young boy neutered and the rat didn't survive. I don't know why.
I believe nanashi was saying her boys are crazy lovable. Not crazy, lol.
My neutered boy is amazing. His fur is soft and free of buck grease. He's lovable, though not cuddly yet. He gets along great with Anya, his female cagemate. He's an awesome shoulder rat. I don't know if neutered changed his personality any, but it did eliminate two things and the possibility of something else. Buck grease is gone, as are the rather large... parts... he had. He also has no chance of developing hormonal aggression, which three of my four previous intact males suffered from. It is also possible that his urine smells less than intact males, but it's hard to know. When I had intact males, I had eight total rats: 4 females, 4 males. And I didn't always keep up with cage cleaning as I should have. Now I just have three rats, two females and a neutered male, so I can't compare.