Which also implies performance benefits over Ruby. I think another way to view it is Go with Ruby syntax (although Go has its own runtime overhead). Their introduction document [1] is a pretty concise overview.
I think it's an interesting project. But not being a Ruby focused coder these days, I can't see myself choosing this over other compiled languages at this point.
It doesn't attempt to be different from Ruby at least in its looks and feel. Crystal strives to be as similar to Ruby as possible. The creator stated some reasons why they created Crystal on the github repo.