It's not great. I've used it, and it's never hurt me, but it doesn't do the job as well as it should. The instruction on the bottle say that you should try it on a small area where you want to use it 24 hours before you use it on the entire area. If you have no adverse reaction, then you can proceed. However, it says to do this every time you use it, because you can have a reaction even if you never have in the past with using it. It can be some harsh stuff.
Salley Hansen has a better option that can be used for sensitive skin, has a brush on the bottle right where the stuff squeezes out, so you can use it without making a mess, you can pop in the shower with it on (just don't let any water get into direct contact with it until it's ready to be removed), and it works much better than Nair. It doesn't have the burning sensation of Nair, too. Still, it has the same directions and warnings on the back for waiting 24 hours after you test an area, even if it hasn't been a problem in the past. But to my skin, it's much gentler.