I use this product mostly as an primer for my eyeshadows on my lids, rather than as a concealer. It works for a concealer, but I find it a bit heavy for under my eyes.
When applying to my lids, a tiny amount is enough, and it blends effortlessly. It also dries quickly, for those of us who don't get up in time to do a full face, yet would prefer the eyeshadow we do apply to stay without creasing. In this, the product works very well. It does indeed help my shadow last 8 hours, at least, without creasing. I tend to have fairly oily eyelids, if such a thing is possible, and this allows me to use all sorts of shimmers and iridescent shades I'd normally avoid.
One thing to note: I have very fair skin and use the light/medium shade. It's possible that this is too dark for me as a concealer, which is why I don't prefer to use it as one. Also, it has some significant yellow undertones, which is supposed to combat the blue shades tired eyes sometimes get, and provide you with a neutral, blank slate for your eyeshadow. It works very well for this. But keep this in mind--I wouldn't wear it alone, or with very sheer shades, as the yellow undertone can look a little strange under some colors.