I did it for a week straight last year, when I ditched my life and wound up meeting up with someone I vaguely knew from discord
I can only think to describe it as blissful apathy. Not a care in the world, and no physical or emotional pain present. Every sensation was pleasure. I can see how people get hooked.
On the flip side, it made me very sick and I filled several garbage bags with puke, and pissing was frustratingly difficult. However I was too high to care.
I would become very agitated when coming down from it - and that there is the addiction aspect, clearly.
I wish I never did it. Ffs it was only for a week and I still think about it sometimes. I don't think I'll ever feel that good again.