From reading the release notes on 12.0 RC1, it looks like he's taken care of some of the common issues with 64-bit, he added the nspluginwrapper for using flash, and it looks like he's gone back to allowing compiling 32 bit binaries. It already allowed running 32 bit, but the last release i had tried for Slamd64 didn't let my compile 32 bit without chrooting, but that looks to be changed here.