There is a regression with version 0.5 at least on FreeBSD/i386 8-stable here: official Apple's Darwin ISO images (from http://www.opensource.apple.com/static/iso/, any version) boot and install just fine on 0.4, but die on 0.5 with kernel panic early in the boot stage. No fix is known. :-(
I am finding similiar problem with 0.5 with linux - and about to file a bug. 0.5 x86_64 linux or 0.5 windows jit under wine both hangs with darwin 8 install.
Various problems with x86_64 for earlier versions (not least no jit, and jit fails with 32-bit binaries), and in the end only managed with running 0.4 windows jit under 32-bit wine.