The magnetic system works great and there are several design options available (and if you must, you can always get a white one and paint it however you want).
Some have said that the plastic decorative case is a little flimsy. Personally I don't find it flimsy at all and regardless, the base board is pretty rigid in itself and doesn't rely in any way on the rigidity of the top cover. The board doesn't feel flimsy in any way when in use. So I'd say if you're considering the plastic top cover, definitely go for it.
What can I say? It's a decorative case. Build quality is great. My fairly new trek into Drop products hasn't disappointed me, unboxing felt very nice and (to me) felt very premium.
It's nice for the opportunity to swap the look of my keyboard fairly quickly. However, a full slot for the USB C cable to slide through would be nice. Right now, you have to disconnect from the keyboard to replace cases. (Minor gripe)
Hopefully more options to come in the future!