Haiku is really very usable - I'd encourage everyone to try it out under qemu at least. It has a Windows 98-ish / Linux early 2000s feel before things got complicated and unusable.
Yeah, I ran it bare metal on a laptop for a while and the only thing that really killed it for me is that Haiku is mouse-heavy and 1. I don't like that, and 2. that laptop had poor mouse input.
