This rating has been hovring between four and five lippies, but after using it for about six weeks I can only give it a five.
It's a thick, sticky, glycerin rich serum with PHAs (5% gluconolactone, 4% lactobionic acid and the odd percentage of mandelic acid). It's not a hardcore exfoliant. You wont peel or flake using it. The pH can't be very low, because I can use it all around my eyes with no problems. I experienced a slight tingling the first few days, but after that - nothing.
There's a world of difference between PHAs and AHAs like glycolic acid. Poly Hydroxy Acids are moisturizing and antioxidant and not the least irritating. It doesn't have that quenching, plumping feel you get from hyaluronic acid products, so at first I was a bit fisappointed in the moisture it gives, but once your skin has shed all it's rough bits I don't need more.
I use it at least once daily, sometimes both morning and night. 1-2 pumps under moisturizer or retinaldehyde treatment. The initial stickiness might want you to pass on putting an extra moisturiser over it, but since it's oil free, drier skins like mine needs some extra emollients.
So far my skin is a lot smoother, feels almost denser, lines are a bit softer, foundation glides on more smoothly.
It has a fragrance with the allergens Limonene and Linalool listed, but it doesn't bother my skin or nose at all.
A plus is that it never pills up whatever I put on over it. Will definitely buy again. This bottle will last me at least four months so to me it's quite affordable.