On the whole, Firefox is a woefully incomplete mobile operating system, and the ZTE Open will only confirm people's suspicions about Chinese manufacturers' poor quality. The ZTE Open costs just $80, but it's not a device for serious use.
The ZTE Open is aimed at developers, though it is sold in Spain commercially as well. It's best to think of this not as a serious smartphone choice even in the developing world but as a proof of concept that you pay to try.
Maybe next year, Ubuntu Touch will be out of beta and competing with an improved version of Firefox OS to show the world that open source can put mobile computing in reach of the whole world. But today, you're better off to look for a cheap Android device whose hardware may be compromised but whose OS can do the basics and more.
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