The question is: is it worth the effort to publish in other stores besides the Google Play store (former Android Market) ?
My two games were published in a bunch of app stores.
My idea (as you may have already guessed) was to spread them as much as possible in order to increase the download number and consequently my revenue.
In fact, I had much more downloads than I would have if my games had been published on Android Market (now Google Play).
The drawback is that each app store has it’s own rules, submission is manually made (and it takes a lot of time), you have to prepare assets for each one and their requisites vary on app store basis. To make thinks worst the submission process of many of them isn’t intuitive. Much on contrary.
All in all I think that (for me) it worth the hassle. In this page you will find a list of application stores I know. This way you will be able to submit you apps and games to as many of them as you want and decide for yourself whether it worth the effort.