While this product didn't work for me (something in here breaks me out), I think it's overall a solid product.
First, I should note that I used this primarily as a face sunscreen, not a primer. I did test it under makeup once, though, and it did not ball up under or dry out my foundation. I can't say if it improved the wear of my makeup because I have very dry skin, so products tend to stick to me like glue.
As a sunscreen, this product worked wonderfully. It has a slight tint to it, but it did not too dark or ridiculous on my very fair skin; in fact, it was undetectable. I think this tint will help prevent a white cast if you're more on the medium/tan side, but I don't think it'll be enough for very dark skin. It has an incredibly smooth, silky feel, similar to very silicone-heavy foundations or moisturizers, and it slides across the skin easily. It felt weightless on my face.
I did not experience any burning or freckling with this product, although I must note that I usually wear a hat when I'm out, which helps. It didn't burn my eyes, either, which is great for a sunscreen! This product doesn't claim to be particularly water-resistant, but I did swim in a lake for about 30 minutes with this on, and when I wiped my face with my makeup remover and a facial cotton later, you could definitely seen the tinted sunscreen on the cotton.
It's a shame this broke me out, because it's one of the most comfortable, cosmetically elegant face sunscreens I've ever tried. If my skin liked it more, it'd be my new HG!