I've been using Etude's Soon Jung line extensively, and I've gone through about 7-8 tubes of this cleansing foam! I started using it after hearing that people with sensitive skin should use low pH products, and it's truly so gentle. Since using this, I've had far fewer blemishes. It's also great for a quick cleanse on makeup-free days. Plus, it's fragrance-free, which is perfect for those with scent sensitivities.
The cleansing effectiveness might be a bit weak if you're relying on this product alone. It's better to use a cleansing water or oil before this foam. Other than that, I don't have any major complaints.
Do some research online and try to find a good deal! I buy mine from online shops where it's sold below retail price. They often offer coupons too, so I always try to use those to get the best price possible. Paying full retail for this can be quite expensive.