I LOVE the cover drops! Once I finish most of my current foundations, I'm probably going to try and stick with using those most of the time. They are just super convenient, and the coverage is great, and the color match is so good, too. So yeah, I definitely think they're wroth it.
One thing I've noticed is that they don't seem to work as well when mixed with other foundations. Usually the pigments bond instantly with anything I mix them into (moisturizer, SPF, serum, et cetera) but when I mix into foundation I get almost the opposite, like after a while on my skin they start to break up. It doesn't bother me, since that's not why I bought them, but I can see this being a downside for folks who wanted to color correct or oomph up the coverage on foundations!