Since there are so many good reviews on here already I'll just TRY to keep mine's nice and short =) I love this primer, you only need a little bit and it keeps the color of my eyeshadow locked in ALL DAY/NIGHT. It makes colors pop even more than normal, and that pop lasts soo long. I bought this because of the reviews on here and it has lived up to my expectations. The only problem that I have with it is that you have to wait so long for the product to get less sticky (about <2min) or else you cannot blend the colors in normally. If you do apply eyeshadow right after its good for packing in colors but you still have to wait awhile to blend. And the packing needs to change! I love how the bottle looks and everything coz its so cute, but you can't get the bottom stuff out, so you have quite a lot left when you toss it. But other than that, no other primer performs the way this does, so to me its irreplaceable and my total HG.
UPDATE: Okay so I solved my packaging problem of the UDPP thanks to enkore's awesome video!! Here's the website: http://www.youtube.com/watch?v=Mkzonbf-3Hs