> What would you hope to obtain that you cannot just by using, say, a customized Linux Mint?

When things are coded right, Haiku / BeOS is blazing fast (every single thing runs in a separate thread), and resource usage is tiny. I think the OS only uses about half a gig of RAM? When the apps are coded right, there's a feeling that this is how our modern computers could have been, free from bloated software and using the full speed of the machine. And when shutdown only takes a couple of seconds, it makes you wonder what the other OS's are doing.

Of course the reality is not that. Display drivers & video codecs on Haiku often don't have the right hardware acceleration, most of the software you need is now Linux ports rather than BeOS native. But Haiku sometimes feels like a calming OS. Because it's so small and quite modular, it feels like an OS you can still potentially get your head around.