Haiku Alpha 3 got released recently!
http://haiku-os.org/get-haiku/release-notes
I've just installed it on my netbook and its looking great - it makes all the other modern OSs look slow in comparison and I'm really excited about where this could go. It boots and runs SO fast even on modest hardware, my sound works, lan+wifi works (no WPA yet though), I can print.. now I'd just like to be able to fire up sunvox and make some music with it!
SDL and gcc are available for Haiku and its supposedly POSIX compliant so I would hope you'd be able to port it pretty easily - I think Haiku would be a very cool platform to run sunvox on and unlike most of the other platforms it runs on Haiku doesn't have any good alternatives to sunvox available - another good reason to port it

Apart from a Haiku port my most wanted feature has to be support for non-4/4 time sigs - might we see this added soon?
Thanks very much for the excellent program!
Dan