Macworld reports that Apple's recent Mac OS 10.4.8 update has boosted the speed of Photoshop CS2 by 34-36% on some Intel-based Macs. Photoshop CS2 is not yet a universal binary application, meaning it must run under the Rosetta emulation mode on Intel-based Macs.
With the previous version of the Mac OS, 10.4.7, Photoshop CS2 ran Macworld's testing suite significantly slower on Intel-based Macs than it did on comparable Power PC-based Macs. But OS 10.4.8 has brought Intel-based Mac Photoshop performance within easy shouting distance of Power PC speeds, according to Macworld's tests. Speeds increased by 36% for the Mac Pro Quad Xeon/2.66GHz and by 34% for the 15-inch MacBook Pro Core Duo/2.16GHz.
Microsoft Word, which also is not yet a universal binary application, is also faster with OS 10.4.8, but the speed increase is more modest -- 3-12% depending on the specific Mac model tested.