I've written a couple things in it, mostly little web servers that serve a questionnaire or something, more recently a Lisp and a rudimentary voice chat. I really really like it. Compared to the languages I'm coming from (C/C++ mostly, some Python & C#) the compile time checking is unparalleled. I frequently find that once I've fixed all the compile time errors the program works first time, something I've never experienced in any other imperative language. The standard library is nice too. It's still missing a couple things, for example hash functions better than SHA1 must be accessed by providing their string names to the OpenSSL module at the moment, but overall it's well designed and miles ahead of C/C++ in functionality. My main gripe is the state of Windows support, it works in the Linux subsystem but I spent three hours trying to work out how, for my voice chat program it involved:

1. Turning on something in PowerShell.

2. Installing something from the Windows store.

3. Adding a new repository to Apt.

4. Installing Crystal and all the dependencies of your application.

5. Compiling your application.

6. Installing PulseAudio for Windows.

7. Connecting PulseAudio for Windows to Linux somehow. (I gave up upon opening the guide for how to do this bit).

Hardly a process an end user can be expected to do.

I'm writing Mint (https://www.mint-lang.com - https://github.com/mint-lang/mint) in Crystal.

For me it is a really good experience: for example the last update didn't break anything and I'm able to add features consistently and relatively quickly.

An alternative front end for Youtube. Not my project:

https://invidio.us | https://github.com/omarroth/invidious

I think it's great. If you're a fan of Ruby it's hard not to like. I'd say it competes with go in many respects. If Ruby is your daily driver crystal is perfect for cases where you need more performance or where non blocking io would be a good fit.