For the test I ran two Photoshop actions on my PowerBook G4 1.5GHz and on my MacBook Pro 2.0GHz. Both are similarly configured with 2GB of RAM and 120GB (5400RPM) hard drives. For the purposes of these tests both machines were booted into clean OS X user accounts with no other applications running. Photoshop guru Will Hammond created the actions and provided me with benchmarks for his TiBook 1GHz with 1GB RAM and 100GB HDD for comparison.
The first action creates a Kaleidoscope (pictured) from and existing image of a bolt. This action has scaling, rotation and blurring.
The second action takes a 10MB image and scales it losslessly to about 550MB. It does so in 110% steps with sharpening in between. To create the 550MB file it tortures the processor, RAM and HDD.
The results are very interesting... (Shorter times are better)
Test 1- Kaleidoscope
PBG4 1.5GHz -> 0:29:59 (0 min, 29 sec)
MBP 2.0GHz -> 0:42:87
TiBook 1GHz -> 1:08:00
Test 2 - Bali Girl
PBG4 1.5GHz -> 2:16:00 (2 min, 16 sec)
MBP 2.0GHz -> 4:03:00
TiBook 1GHz -> 6:45:00
There's a pretty big performance hit in Photoshop CS2 with the MacBook Pro when compared to the Aluminum PowerBook G4 due to the Rosetta emulation. MacBook Photoshop performance falls somewhere between the TiBook 1GHz and PowerBook G4 1.5GHz.