I have used this language for a few things (csv parsing and some simple personal cli tools). Other than the normal pre-1.0 issues it's great. I wish it had a tagged union type, but it looks like that's planned based on the github issue tracker.
It is a pretty big improvement on C without changing the ABI. Maybe not the improvements I would make if I was smart enough to make a compiler, but better than doing C which I also enjoy despite it's warts.