I really like Crystal, and while it hasn't reached a 1.0 yet, it is still great and used in production. I think the main selling point of Crystal is performance + nice syntax. The docs are great and will help anyone curious to learn Crystal along the way. Crystal's biggest problem is that it doesn't have the support of a company or a large base of users so the core team isn't funded as much as they'd like. All in all, I think it is a great language!