One thing I'm never sure about with these functional frameworks is memory allocation. They seem to create new objects willy-nilly, rather than reusing. Measuring performance of the counter application showed 11Mb garbage collection after about 30 clicks, and that's with one of the smallest state objects possible.

I can see this being of use for apps where this kind of performance is not critical, but when you're animating things this will cause jank. Would love to see an example with a much larger state, and fast updates during animations.