I've been involved in Node.js and the broader JavaScript ecosystem for about 5 years now.
It's super mature with a large ecosystem. The de facto standard for web frameworks in Node.js.
Con: you can find yourself with a mess of spaghetti if you're not cautious and thoughtful about organizing your code, route handlers, and middleware.
Same folks behind express, but able to make some different decisions and use some modern techniques. It's still mature and stable, but with a smaller ecosystem.
A mature framework for building storage-layer agnostic realtime applications.
There are some pitfalls with coupling your client, API, and storage tiers too closely together, but it's a solid choice for rapid development of realtime applications.
A strong choice for IHers, depending on your application's needs.
If performance is your thing, look no further. This is the dominant Node.js framework focused strictly on performance.
It's not as popular as express or koa, but still a mature choice with a reasonable ecosystem to build on.
If you're still here, I've written my take on 10 frameworks here, with lots of links and more recommendations.
Comment below with questions, disagreements, and stuff I've missed. 👇