I will admit that I've had this product for a little over a year, but haven't used it a lot. I first discovered it before I knew of Urban Decay's Primer Potion, which overshadowed it after I got my NAKED Palette.
The whole idea behind Benefit's Lemon-aid is a primer, brightener, concealer and colour corrector all wrapped up in one. It's a pale yellow which helps counteract the appearance of veins on your eyelids.
In the pictures below you can see the product swatched on the veins of my arm. I think it does a great job at brightening my eyes and concealing discolouration, but it's not so great in the priming department. I have very oily lids and this product doesn't help whatsoever.
However, if you are looking for a new primer and want to give this one a go, I would recommend concentrating the product on the expanse of your lid near your lashes and above your crease, blending the two together in the socket. This technique allows me to use this primer without the fear of creasing!
Overall, I wouldn't recommend this primer. I feel like the UD Primer Potion does a much better job at keeping your shadows in place and also makes your eyeshadow appear more vibrant, eliminating the need for colour correcting. Though if you do enjoy this product, please leave a comment below, I'd love to hear your opinion!
Have a lovely day!