Like the blog post says, people have already made their minds up about whether or not Ruby is fast enough for them, and incremental speed upgrades, or even faster languages like Crystal that market themselves as Ruby-like are irrelevant in this decision process.
For the majority of us who use Ruby, we use Rails, and Rails is great. Crystal is irrelevant as a comparison to Ruby, because there is no Rails (I'm sure there's web frameworks, but they're not nearly as productive as Rails). Rails isn't perfect, and there's plenty of room for improvement, but switching languages and starting from scratch isn't the solution.
The biggest downside of Ruby compared to other languages (besides speed, but like I said, that doesn't matter here), is lack of static typing. That may or may not be a problem depending on your usecase.
I wouldn't say it's irrelevant, Crystal is already being used by ex-Rubyists and the ecosystem of crystal libraries are being built by them as well.
After 1.0 you would see more of this happening.
Lucky [0][1] by Thoughtbot is the closest to Rails in the Crystal world.
> The biggest downside of Ruby compared to other languages (besides speed, but like I said, that doesn't matter here), is lack of static typing. That may or may not be a problem depending on your usecase.
Then I shouldn't see any complaints about speed on Ruby if it doesn't matter, Crystal solves all of this built in, with the trade off of slower build times, but then again Rust also has slower build times as well.
But to each their own.