This has become interesting to me: I have the PB in my sig. In the morning when I start the PB and open my apps, I will have 219MB of RAM used and 805MB free. As the day goes on to the evening, I will still have the same apps open, but my RAM will be something like 410 used and 590 free. Whats with this? Is OS/X not very good with letting go of memory if you use other apps?