I like Haiku. In my experience, it has most responsive window manager for any operating system that runs on 90s-00s hardware. I think it has a lot of potential, but presently, I’d describe it as an alternative to something like Chrome OS. I wish the web browser situation was comparable to Linux, macOS, and Windows.

I should admit that I have an academic interest in operating systems and Haiku, for a variety of reasons, is exciting (e.g. it’s a functional open source operating system that isn’t strictly POSIX).

Except... Haiku is POSIX? The POSIX compatibility isn't just some compatibility layer, it goes all the way into the kernel. We use the fork-based process model, POSIX filemodes, etc.

Yep. Totally fair. I edited my comment to say “strictly POSIX.” Is that a fair characterization?

What does "strictly POSIX" mean, and how does Haiku not meet it?

If there are POSIX APIs we don't implement, it's simply because we haven't gotten around to implementing it / nothing needed it so we didn't bother, not because we are explicitly avoiding said APIs.

Ah, I wasn’t aware. Thanks for the correction! :)

What more specific response do you want? "Personal computing", i.e. use as a "daily driver", is the entire reason Haiku exists.

So, exactly the same use cases as Windows, Mac, Linux desktop?

More or less, yes. We have our own philosophies about data organization and management and the like, but largely, we are aiming at the same market.