Yes, pretty much what nvtwatch said. It's similar to having a bad sunburn in places where you'd never get sunburned (well, most people wouldn't). Red, burning, itchy but if you scratch it it hurts. Takes a few days to get over it. As I've said elsewhere, as one who loves sitting for hours in wet / poopy diapers I've accidentally gotten it a few times but not for 15 years because I'm now very careful not to. Sometimes this involves ending the "fun" before I want to, but it's OK.
I find it interesting that some people's skin seems to be very resistant to it while others (like mine) seem to get it very easily. Also, I find that wearing poopy diapers makes me way more prone to getting it, must be some bacteria present that makes it worse.
The last time I got it I used Dessitin ointment for a few days and that helped. But to get this I had to put on my underwear and pants (which was NOT pleasant!) to go to the drugstore. I remember standing there paying for it, it hurt and I kept fidgeting. Wouldn't surprise me if the lady cashier realized that I wasn't getting it for a baby, rather, was getting it for ME.
Possibly getting diaper rash is why I'll never go 24/7, and why the longest I ever wear my diapers anymore is from around bedtime (9-10pm) until around noon the next day. Then I always get out of them, take a shower, and dry out for a while.
All that being said--I understand wanting to experience it, even just once. It's oh so very babyish to have to look at yourself in the mirror and admit that you wore your diapers so long that you now have diaper rash! But if you do it, don't say we didn't warn you!