I really haven't used any other sculpting material other than hardened globs of "Elmer's Ultimate Glue", so I have no actual anything to compare this stuff to but to me its pretty kick ass.
Paperclay doesn't actually contain any clay its just this weird malleable lump of white clay-like stuff, that is composed of paper byproduct I believe.
It says it needs like 16 hours to harden but so far I've sculpted limbs and heads out of it and it can harden pretty quickly like in a quarter of the time on average. Its pretty durable until you moisten it again, which is nice because you can smooth out any cracks due to shrinkage from drying, or sculpt over/resculpt something to your liking. Downside is you need to basically seal it or coat it well with paint to ensure it doesn't get moist again.
It says to change its color is to add a few drops of paint to it and work it in until you get the right color you're going for.
I paid about 6 and change for it at Michaels for a pound of material and I'm pretty happy with it as I'm pretty new to the whole sculpting game.
Yeah you have to get the figure nice and moist where you want that stuff to stick or it comes off. I find a nice room temperature glass of water does the trick. Not too cold not too warm. After that it bonds really nice like. Hell it takes very little to sand it. Pretty sturdy and VERY light.
heh heh