A news flash on OSNews linked to a post of a planned series by Wesley Moore on his quest to find a replacement to OS X ( http://bitcannon.net/post/finding-an-alternative-to-mac-os-x/ ).
All but one investigated replacements were derivatives of UNIX in one form or the other (FreeBSD, Linux, or UNIX-Like).
Here is what he wrote about Haiku in his list of worthy alternatives: "Haiku – So much promise but just can’t quite seem to get the momentum to be a viable option.".
Hoping he will keep monitoring progress and re-evaluate Haiku once R1-Beta is released.