I have used these a few times and find them adequate if not stellar.  They are small and they do sort of release a lot of powder when you first pull one out of the tub.  The tub isn't super functional, but they do work reasonably well.  They are no match for doing the job "right" with polish and whatnot, but are good in a pinch.  I will likely keep some of these around for those morning rush jobs.