I can give you some idea. I've had two surgical procedures where something like midazolam was strongly recommend, but opted out for one of them. The one I opted out of was a four hour procedure sawing on bone and soft tissue.
For the procedure on midazolam, I have virtually no recollection of the procedure except for about a minute in the middle where it apparently wore off. It was a completely neutral experience.
For the other procedure, it was extremely unpleasant for two reasons but I got through it like a stoic. First, they had trouble keeping up with the local anesthetic, too many nerves involved, so there was quite a bit of transient pain and it got sloppier over the length of the procedure as the doc got tired. Second, even when you can't feel pain, you can still feel them tearing up your tissues and rearranging your parts, which is disconcerting if nothing else. Overall, I strongly recollect just how unpleasant and painful (even under anesthetic) that procedure was. I probably would not be able to tell you any of this if I was on amnesiacs because I would not remember.
It is really about where your thresholds are. Like you, I find the loss of memory on the amnesiacs disturbing and the alternative, anecdotally, was far more unpleasant than I think some people imagine. The experience that I remember doesn't bother me that much because that is my nature but I can't deny that I have vivid memories of it. I can easily imagine that many people would prefer to not have those memories. That said, I would likely elect to forego an amnesiac again if I thought it would inconvenience me (i.e. by making you useless for several hours). I can deal with the experience.