It gives a genuine instant refresh: Every time I use it, especially in the morning, my skin immediately looks more awake. It contains glycerin, so it leaves a really nice, hydrated dewiness behind rather than stripping my skin dry.
It can sting the eyes: There is a light citrusy fragrance in some versions, and between that and the Vitamin C derivative, it can occasionally tingle or sting a bit if I get too close to my waterlines.