I can't see what Haiku offers that modern OS X doesn't. Drag and Drop between applications? Got it. Combining soundcards to use in aggregate? Got it[1]. Object Oriented APIs? Had it since NeXTSTEP (and they're called 'Kits' as well). The only thing that seemed mildly interesting to me was the routing of audio between apps, but this is mostly achieved these days using ReWire or Soundflower (admittedly not an ideal sol…
Haiku isn't a memory pig- I'd like to see that ideal come back in OS design.
And yes, I am transfixed with 'memory sucking pig' as a phrase right now.