I wonder if we are not "over rotating" on the memory question here. I have 2.5 GB of RAM in my PowerMac G5, and also a memory usage meter running in my Menu bar (MenuMeters, if any one is interested). With Photoshop CS2, Thunderbird and Safari all running at the same time, I never get more than 2/3rds or so my total memory used. My guess is that 2 GB is just fine!
Can anyone who has used their MacBook Pro with 2 GB, then upgraded to 4 GB, provide us with any insights as to whether it really gets any faster? I am dubious...