Probably two of the most overused items in the beauty blogosphere, but I only recently started playing with them.
I'm using Milk mostly as a base/highlight, and Black Bean on my upper lashline for a smudgy/smoky effect. On Tod these crease really, really quickly. Most creamy products crease on her, so it's partly the way her eyelids fold, but I do think the creaminess of the product has something to do with it. These don't "dry" exactly - you kind of blend them out until they become a thin wash of colour. I wouldn't ever use these just as eyeshadow since I don't ever wear just black or white eyeshadow across my lid, but they're a convenient way to pump up colours or duochromes.
So I tested three things for you over the shadesticks - from top to bottom: a pink eyeshadow from the BH Cosmetics 120 1st edition palette (all swatches here); a mineral eyeshadow from the Bella Pierre 9 Stack (all swatches here); and a MAC Pigment (the name's rubbed off and I can't tell which one it is, sorry!)
They're not bad! Black Bean gives the pigment more depth and smokes out the eyeshadows, while Milk makes the colour more true to pan. All in all, not bad for $6!
PS: be careful with these - I closed Milk a little too enthusiastically and the cap split with little to no fight. I can't even look at it anymore.