I tried it on my PC. There is obviously not enough available software to be a real daily driver but it struck me as an OS that would be very enjoyable with low connectivity needs like typewriter and mail.
I loved how coherent it felt : the UI, the base software and even the filesystem. If I understood correctly, the filesystem is a representation of all your data and « files » can have arbitrary metadata and you can do pretty much everything from the file manager. It’s like your whole filesystem is a nosql database and apps are ok with that. Your contacts are « files » in a folder, your mails are « files » in a folder etc …
I never touched BeOS back in the day and I can totally see how this paradigm could have worked well in the 90s with low connectivity. Being able to write a mail « file » without internet, drag and dropping it onto a floppy drive and then on another computer, sending it over the Internet and everything with the file manager. It felt amazingly coherent.
Unfortunately this paradigm ceases to be useful when you need interoperability with other computers that aren’t compatible with BeOS/Haiku filesystem which means statistically _any_ computer.
But on your typewriter machine, that could be interesting.