Paula's Choice

This product is really great - it's one of those few rare products, where you genuinely can see and feel a difference after the first use. This for me was not at all irritating (although I wouldn't recommend applying this to broken or irritated skin, it'll make things worse!), didn't dry me out or cause any negative reactions. It made my skin a lot smoother to the touch and brighter (however it did not prevent or help with my blackheads/whiteheads). It also helped to fade my discolourations faster. I would highly recommend this product, however because this is an American brand/political reasons I don't see myself repurchasing anymore.

My skin is too sensitive for this serum. It left me to feel like my skin was burning.

This broke me out, but it did feel comfortable on. I had no issue with a white cast, but I do have fair skin. I will not repurchase.

This is just standard 2% BHA, but in a spray bottle. It's not really cheaper than the facial BHA exfoliants that PC has either.
But hey, 2% BHA is going to work for acne if you're patient. I've struggled with bad bacne, sometimes some intense painful bumps. By applying this on my back twice a day, my bacne has greatly diminished. I sometimes get a little bit stil l but it's down at least 80%.
The marks and scars though will require something else.

This is a nice serum, but I'm not sure how much of a difference it made to my skin. In fairness, it's meant to be for wrinkles, and I don't have many wrinkles yet. But I was hoping it would help with other skin concerns (namely evening out my skin tone and fading scars), and it didn't really. It did make my skin feel firmer/plumper and better hydrated, however. And that's not nothing. It's a very silicone-y serum, which means it spreads easily but also feels a bit greasy. I used up my bottle and may give this product another chance down the line. This cost $42 USD for 1.0 fl oz, which is a little steep but still competitive within the space. And you can frequently get it cheaper thanks to Paula's Choice's excellent sales.