I have terrible under eye circles so I was excited to try this out. The yellow goop seems too watery and didn't really cover up much. Then when I put the concealer over it it seemed to completely wipe away all evidence of the yellow neutralizer, leaving a thick concealer that is a little too bright for my skin tone. Also, the little roller ball is pretty pointless... and it also hurts to use. The ball doesn't protrude enough so the edges kind of scrape your skin. And it's just not soft enough, I think, to rub against the delicate skin of your under eye.
I do sometimes grab the concealer part of this when I am in a rush, but I don't use it to it's full potential otherwise. Maybe one day I'll give the yellow goop a little more time to dry and try it again, but my initial reaction to this product was lackluster.