Error management through Option values, the borrowing checker... they are cool technologies for a C-like language, but they are not palatable at the beginning (maybe they are an acquired taste like beer?). I am tempted to stretch it a little bit more and see how productive I can become writing Rust code, but also not so sure about the effort.
I think the bit about productivity may certainly be true if you have to use libraries, obviously Ruby has many more available now (maybe forever), but I certainly feel more productive in Crystal now, maybe for things other than the language itself, admittedly. For example, producing a binary makes installation a breeze, and I don't worry about which version I'm running as I point the right compiler at the code; no Bundler now, library installs are sane (at last!); and socially I find the lack of "rockstars" in the main team refreshing, I have no fear of being dissed or dismissed, it makes contributing easier.
Surprisingly, Crystal seems to be much leaner in runtime size than Rust, with similar performance (although the use case is so simple that even good old Ruby is fast enough).
But then again, I feel you cannot beat Ruby in terms of dev productivity.