Valve, the company behind game distribution system Steam, has warned that Mac users should avoid upgrading their operating systems to 10.6.4 if they have an Nvidia graphics card.
Valve is currently working with Apple and Nvidia on the problem, and a fix is imminent, apparently, but we have found that upgrading to the latest version of the Apple operating system causes severe malfunctions in even slightly older games like Half-Life 2.
In our experience some games become jerky, unresponsive and nigh-on unplayable.
Steam has openly admitted as much in a forum post which says: "The recent 10.6.4 update from Apple has noticeable performance issues for Nvidia graphic chip owners running high performance games. If you wish to avoid this, you should consider waiting to install the 10.6.4 update until Apple has had the opportunity to address this issue."
Even before the OS X upgrade, users had noticed a significant disparity in performance between Mac and Windows versions of the same game, with benchmark figures showing that the Mac versions had much lower frame-rates on comparable hardware.
The inconsistency was originally blamed on immature drivers and modest performance improvements were promised with the release of OS X 10.6.4. So much for that theory.
Apple was about as unresponsive as the average Steam game when asked if it could give us a date for a fix.