This is an interesting way to take a vitamin D supplement. My doctor has recommended taking a D supplement for some time and my levels are measured regularly. This product seems to work fine, but I don't really see much difference in my results vs. the traditional yellow gelcaps. The taste is something like a Dr. Pepper reduction – possibly due to the peppermint oil, but if you don't want it straight up, it easily disappears when mixed into your favorite drink. Possibly the liquid is quicker-acting and it matters if you are taking a dose before an athletic event, but for most normal people, the traditional yellow gelcaps that you can buy cheaper in bulk quantities should be sufficient to maintain good levels of D in the body.
For the price point, I would have expected to see this product USP-certified, which assures quality, purity, and potency. GMP just means they have good manufacturing practices in place to produce consistent results and that one tablet, for example, is not substantially different than another. It's a subtle difference and is confusing, but pricey supplements should have both certifications.