How do you define whether a product works? Well, you could start with a negative definition: if said product is only capable of generating satisfactory results if put to use in a perfect environment and in the process uses up 2 to 5 times the estimated resources, I would call it a complete failure. The Esbit Kaffeekocher is exactly that type of product.
Quick description: the Esbit Kaffeekocher is basically a cafetera (we all know them from Italy). It is intended to be used with the Esbit dry fuel cubes. The producer claims it is possible to make a cup of coffee with a single fuel cube.
Pros: the retro-industrial design is pretty swell. It makes you really want to taste the coffee that comes out of the fancy nozzle. If only it ever came out. Oh, if you use the Kaffeekocher in your kitchen at home, at some point (my personal record was two fuel cubes) it will make a decent coffee.
Cons: it weighs a ton, serves no other use than making coffee and by default, it does not fit on any other stove than the one it comes with. Find a campsite with a community gas stove? No coffee for you, unless you build some impractical and potentially dangerous workaround. Esbit claims the Kaffeekocher is not safe for use with any source of heat other than their proprietary fuel cubes. Taking into account that under normal camping conditions (read: outside the secret underground Esbit laboratory), it takes a whopping 3-4 cubes (an optimistic estimate) to get some coffee out of this thing, that cup costs about 2-3 times as much as a fresh and steaming espresso at the next café.
Verdict: save your money and get a system that works with boiling water (Bodum makes a french press for camping, for instance).