That's a fair point, however it seems that if it were an OS issue it wouldn't be restricted to one processor.  Also, earlier today I built a bottle that had SSSE3 extensions for someone with a Haswell model 4 and it failed spectacularly, causing runtime crashes and preventing things that depend on Qt from compiling.  So I built him a bottle without SSSE3 extensions and it worked fine.  That suggests to me that it may well be both a runtime and compile time issue.

But yes, it's only been reproduced on 10.9 (I don't think anyone with a 2013 machine would be mad enough to run anything less within a week or two of buying it :-P).

I'm happy to do it either way though, to be honest.  I have no preference.  I just figured it might be safer to just blanket disable SSSE4 on the Haswell model 4 at least for this formula.  Your call :-)