I think Rosetta is using just one processores. As a Mac user, I don't use Rosetta that much, except for old verson od DAZ products installers.!
Also, I didn't expreienced all those problems you had with my Masc - I just got troubles with PC and Vista, but now I moved to 7 and got no writing displayed in the window  just once.
It depends on experiences, mine tells that  OS X is better in terms of performances for carrara ;°

 
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Holyforest,
Hundreds of shaders for Carrara