Amethyst is getting towards a useful base feature set really quickly.
When I looked at it about a week or so ago it didn't have the View portion of MVC, so I'm hoping the project keeps on going with the speedy addition of Rails-like functionality.
As for Crystal itself (a new statically type-checked, compiled, Ruby-like language), I look forward to using it more when its a little more complete, as the language is still in flux, and only at version 0.7.x.
I did some playing around with Crystal at the weekend, mainly by investigating what it would take to convert a couple of pure Ruby only gems to Crystal. I was stymied somewhat by the Crystal standard library still being a work in progress, for example classes such as Array still need some work if the eventual aim is to provide a similar set of methods to Ruby itself (e.g. the pack method was missing) , and bindings for common libraries like zlib don't seem to exist yet. However, that is no criticism to Crystal - its simply due to the newness of the language, and will undoubtedly improve as more people start using Crystal and contributing.