Minor flaws there yet: The powder compartment is very small. From my powder going up to 4 scoops (approx 15 g) into it. This is sufficient for me for 300 ml liquid. The container for the powder could therefore be designed slightly larger. The shape of the drinking spout (oval) is used to. As stated above you should also definitely shake the shaker overhead. The lid on the drinking spout and this is seals hollow inside, so that it may settle during transport or later the shake powder that when opened then fall out. However, if you shake overhead liquid is also in this cover. Finally, one should take a slightly soluble powder, otherwise powder residues may remain in the container, but this is not the case with my powder.
All in all, it is a good shaker and the price of 9,90 Euro is OK. I think it's currently the best alternative if you want to transport powder and milk and cook wants to shake fresh.