Hmmm... I will offer up my opinion of the new Universal Binary SC4. Well... menus, scrolling, and general game play feel a touch faster. But, the game now crashes unexpectedly -- sometimes when when plopping tranist-enabled lots... sometimes when plopping parks... its totally unpredictable.
BTW, I am running SC4 on a new 24" iMac (1 GB RAM, NVidia graphics card with 128mb). So, my machine isn't THAT much of a slug (considering it is newly minted and the game is... well... 5 years old!).
Hope that helps -- maybe someday we'll actually be able to run things like all those Windows users out there.
**ALSO** Maybe someone out there could do a comparison of all the different graphics settings for maximum speed? OH OH! One more thing, I used to be able to select "software rendering" but now it will only allow me to use the "hardware rendering" option... who honestly knows.