Looks nice!
How would I do something like an Ajax request when the component did mount? Am I even supposed to do that using recycle or would I have to fallback to classical react components in order to achieve that?
What exactly is wrong with modules like through2? IMHO they are just tiny wrappers, which make handling streams more enjoyable. These are the stream modules I usually use in my projects: through2, from2, end-of-stream, pump and duplexify. Some of them handle some weird edge-cases, which would really not be that much fun to implement manually each time.
Here is also a nice collection of stream utilities: https://github.com/maxogden/mississippi
IMHO one main point of HyperScript (versus JSX) is that you don't need a build-step in order to use it.
I get it that compiling it will bring some performance benefits. Some benchmarks would be nice.
The CSS solutions in React are really fragmented. Every few months there is a new hotness in town. Reminds me a bit of all the Flux-like libraries which existed in the pre-redux period. Personally, I tend to just use plain CSS with some BEM notation. I know, it's old school, but I'm sure it won't be outdated in 5 years from now. In the company we are settling for styled-components though.
IMHO it's fine to use 'in' in JS. As long as you know that it checks for the existence of a property, regardless of the value set. And also be aware that it checks properties in the prototype chain as well. If you don't want that behavior, use hasOwnProperty() instead.
Looks promising. Now the ecosystem around it just has to grow :)
I like that you have chosen the simple and explicit set-/get-method approach over the "convert data into some magical thing with non standard arrays and stuff"-way.
It makes absolutely no sense to build a static website like that with react. If anything, they should be applauded for making the right decisions. Although I agree with tracker1 that having a set of VS Code extensions would have been nice too ;)