I've built a system 1 board. It worked great, minus the long boot time. They ship to the US, but you need to order parts separately. Soldering the surface mount chip was a pain. The main thing to understand is that this is just their hobby project. Documentation is sometimes out of date, the original BoM I got was wrong, etc. No big issues, but it necessitates emailing back and forth which is slow when one party is in Germany.
For the price and flexibility though, it can't really be beat. I ordered two more boards recently, need to assemble them now.