Normally I would be at some fancy event with gorgeous blondes hanging off both arms and one or two attached to each foot regaling the crowd with my newest Theory of Everything, but you get bored doing that several times a day, so I built 10.0.4 instead now that Mozilla has finally seen fit to tag the branch. One of the changes Mozilla dropped busted the build, so that is fixed in the changesets. Please test it out before resuming your use of 12.
Speaking of 12, the failure on Acid3 is due to issue 146, which is an endian problem in the Open Type Sanitizer introduced by Mozilla bug 712217. It affects most downloadable fonts, in fact; you could get around it by disabling the OTS in about:config but I would really discourage that since the OTS is there to protect you from malicious or iffy fonts. The fix is pretty straightforward and I will push it upstream since it probably also affects SPARC. If I respin 12 it will be in there, otherwise 13. It does not affect 10.0.x.
Release notes and architectures: