I feel bad for when I drop them off, while they wait for the before anesthesia part, but after that they are out, in recovery and on medication, and then on medication so not in pain after and pretty gorked out. And I have seen dogs a couple of hours after their neuters back in the kennels at the vet office and they are bouncing around looking for attention.
I don't feel bad about restricting activity for as long as is needed, which apparently is not always the case as you read about giant seromas in the incisions and scrotal areas!
I did ask with my one dog if I could stay in the lobby throughout her surgery as I had told her I'd never leave her somewhere and they let her stay out in the lobby with me until right before her surgery, and I stuck around until it was time to take her home. That was probably the best scenario. I also tell the dog what's going to happen, that I will be back to get them - helps me.
I also do as many pre-check things as possible to lessen my nerves - blood work, bleeding time test, MDR1 precautions as needed for the meds used (I think Buster's list is what I bring? http://www.busteralert.org/
), check off fluids as requested, and have a list where I note anything special. I am also sure to take them off supplements earlier (a week at least) as they can have a bad impact on bleeding and other things in a surgery. http://dogaware.com/health/surgery.html#before
I won't leave a dog at the groomer and have had to work hard to find a groomer who would agree to that. In exchange, I will help brush the dog out.
With her I also have the excuse it's a 30 minute drive, so I'd be driving 2 hours...