I applied it once every week or every two weeks. I started off with leaving the peel on for only 15 seconds, then 45, then 1 minute and 30, and then 2 minutes. I used it a total of five times over a period of two months. I didn't experience any adverse reactions, except some irritation and some redness, which disappeared after fifteen minutes. I'm going to take a break from this product for the time being, because the instructions say not to do too many peels in a row. Also, I would like to try some new products.
I think that this was a fairly effective peel. I definitely think my acne scars/dark spots are lighter, and that my skin is in a better condition. This did not really prevent any minor break-outs, but I think they did make some of the small bumps on my forehead disappear. It didn't make my skin worse, or have any real negative consequences. I've tried to limit the new skin products I've used in the past two months, so I think that the improvements to my skin (better glow, softer, less hyper-pigmentation) is mostly due to this product.
The process was also fairly easy. You have to wash your face twice (with a mild, non-exfoliating soap). Then, you use a cotton pad saturated with alcohol on your face, twice. Then, you swipe on the gel peel with another cotton pad, and leave it on for the prescribed period of time. After the time is up, you rinse your face in cold water for a long time. Dry, and apply a mild moisturizer.
I feel like this review should have some sort of disclaimer, since it's an acid peel. It should be obvious, but disclaimers exist for a reason, I suppose. One should not use this product without carefully reading the instructions and consulting a medical professional. One should follow the instructions to the letter, do a patch test, and remove immediately if discomfort occurs, etc, etc. Anyway, don't be stupid, you're putting acid on your face. I read a lot of reviews on Amazon that complained about this product, and the reviewers clearly did not follow the instructions.
tl;dr: Good value and worth a try if you have dark spots and want your face to have more luster. A fairly easy process, but make sure you do a patch test and follow all instructions carefully.