As the others have said, it looks really interesting. I like the idea of a integrated game controller but for $300, hmmmm not too sure for what looks like is basically a Win10 netbook. But good luck to them I hope they achieve their campaign goal.
Yes, the RetroPie project is a pretty good example of one to try:
http://blog.petrockblock.com/retropie/
pretty straight forward to set-up. I've used quite a few times now on various emulation projects.
I've been hoping Olimex would bring out something like this. I think its the same Allwinner H3 as the $9 computer. As for the RPi Zero I've got ReproPie & EmulationStation working on mine with a custom controller board. I'll post project details if any one is interested?