ב''ה, I do not have experience with barbs unless they were in any surgical anesthesia I've ever had (and these days they usually start with an IV benzo as probably supplanted any for safety), but both benzos and barbs are GABA A (that's GABA subscript A) agonists.
Well, really benzos are purely modulators, hence their relative safety (hit every BZD receptor in the body and you may still be breathing), while barbs somehow go to actually acting like GABA at the GABA A receptors, as can take that to the lethal levels of sedation.
So, same receptors same effects, I'm going to call it "drunk without the mess," and expect that the two drug classes feel fairly similar.
Meanwhile, if you ever get your hands on a GABA B agonist (Phenibut), I certainly seem to have survived that one repeatedly but something about the B receptor *does* allow for the horrible vertigo and hours and hours of empty stomach drunk spins upon withdrawal.
With benzos and thus probably barbs, aside from any issues from not breathing during if you did not, it's just "the good part of being drunk," into somnolence, and should you wake up after the nap, maybe some grogginess and eventually rebound anxiety (far later unless something really short acting like Xanax), and not saying your cognition won't be beer-goggled but that's rather hard to notice while cheerfully GABA A'd up.
So aside from any issues of taste/irritation if oral as doesn't seem to be too much problem, I'm going to say this really would be very pleasant. With an IV benzo push for surgery you perhaps get almost a minute of "yay, thanks doc," before it goes all the way to not keeping the eyes open. (Of course then other anesthesia is used to maintain full sedation to actually being operated on so don't get too clever knowing that.) I really don't know and don't want to think of the IV characteristics of N as might be a can of worms (obviously some folks have had for non-lethal reasons, so does it have a sensation or is it fully pleasant?), but if it's tolerable orally.. the actual drug effect should just be like the deep pleasant sleep of a benzo "but moreso," where the moreso includes suppression of the life sustaining autonomous stuff after complete sedation.
It probably really is the 'fully automated luxury' way to go. If you want to get all fancy or have an actual chronic painful condition, I'm sure taking a known preferred amount of opiate/opioid pain medication with would probably further enhance the pleasantness.