Documentation is definitely not the language's strong point just yet, but that's understandable when it's still on a 0.x release and it's a massive work in progress with ambitious goals. The reference is useful at a high level, the autogenerated stdlib stuff is highly hit and miss and I suppose will be ripe for community contribution when the method of generating it is nailed down.

The language itself is fantastic once you get a decent grasp of it, which you'll probably achieve by reading the stdlib source to get a feel for what you need to do.

I've been using it to build stuff on my Pi Zero. Still hit a few snags with cross compilation and C interop, but it's been a pleasure to write. I'm definitely keeping an eye on it as a good alternative to getting into Rust.