Armen was delighted to see this today. So was I.
This is still just a very very very early experimental build, but with that disclaimer, if you want to try using it, you can get it here. There are lots of open questions about compiler versions, toolchain, mozconfig settings, etc, which need to be figured out before we start imaging up infrastructure like we have done for OSX10.6 64bit and linux64. However, it is great to finally see some concrete visible progress after all the work put into this.
Many thanks to Makoto, dmandelin and danderson for their help to Armen so far. We’ve a long way still to go, so any help would be GREAT! If you are is interested in helping, or just following the blow-by-blow details, have a look at bug#558448.