Argoon: I agree with gegezerg even tho I comprehend why they have to still open the other stores, but is not ideal! Is not radically different from having a shortcut for a non GOG game, like steam has for non steam games, they still show up on your library and you can tag them and all, is not different.
So we can't say, is fine let it stay like that, that is not how things improve for us the consumers.
Perhaps some day by entering in agreements with the other stores we will not need to have so many stores installed, lets hope they are able to pass above their differences.
You're right that the effect is not too different from adding non-Steam games to the launcher. However, this is done in an automated fashion, with metadata and images and grouping matching games. Plus, you see your whole library of uninstalled games, as well. Something you can't do on Steam.
Of course there is always room for improvement, but in the current scenario I think if I'm going to be supporting on store/launcher over another, it's the one that proudly fights for DRM-free games and open-API's.
(I can tell you no other store's launcher has a plugin API!)