Almost no death is truly peaceful, even in cases of death by gunshot or jumping some people end up convulsing in the ground for a few seconds or even minutes. We have to accept some level of discomfort even with the most peaceful and tested methods.
I've tried some of my N in a extremely small amount to see the effects and drowsiness, it tasted absolutely horrible and the feeling of sedation was overpowering, and I'm someone with a high tolerance for these kind of substances that interact with GABA, like alcohol, benzos and many others.
If I were to compare to one of those substances, I'd say that it was as euphoric and sedating as a high dose of alprazolam, but with a heavy feeling on the body, definitely not unpleasant. Maybe the person who survived 6 g of N and described it that way just was not used to that effect, or it was someone with a natural tolerance to barbiturates , I can relate if it's the latter, since I have a bit of a natural resistance to opioids and rarely get high on them, I only get nausea and dizziness and almost none of the euphoria.
However, even if it was as unpleassant as people describe it, I would still take it over any other method, even F and H, and specially over SN which takes more than 20 min to finish you off.