Currently, a widely reported bug prevents the Mac version of SimCity from running in full-screen mode. Some players are unable to complete installation, rendering the game unplayable. For Mac users, the problems encountered thus far seem to stem from technical hiccups, rather than the server-side issues that plagued the Windows version after its launch earlier this year.
EA Maxis has acknowledged the reported problems in a recent update, and has suggested solutions for affected players.
[Update: A Maxis spokesperson has contacted Joystiq, noting that many of these problems were fixed in the game's latest update. "We are pleased to advise that the installation-related issues some players experienced with SimCity on Mac have been resolved," the spokesperson said.]