It sounds like a good idea doesn't it? A primer for your eyeshadow AND your undereye concealer.
Unfortunately, to put none too find a point on it, this product is absolute crap at both functions.
First, even after shaking it for ages, over several days, the damned thing still excretes an oily siliconey liquid before popping out some lumps of brown clay-like material.
When you've managed to smooth this over your eyes, initially it does even out your undereye circles and if you have pigmented eyelids, would probably help those too.
This is where it gets even crappier.
It not only doesn't help eyeshadow to stay AT ALL, it makes your undereye concealer look even heavier and cakier. It's supposed to prevent fading and caking!
Bottom line is, don't waste your money on this garbage. I'm deeply disappointed in Benefit for having put out a product that is this awful.
At full price, it's US$26 - expensive for a primer, INSANE for garbage.
Thank goodness I got it as part of a kit with a mini cream eyeshadow and a mini tub of erase paste. Neither have been superbly impressive but neither have gone straight into my bin either.
Definitely stay away from this one.
Note (Sept 27, 2012): Have contacted Benefit Customer Care about this three days ago and have received absolutely no response.