I was jailbroken with 2.2.1 and just recently updated to 3.0 and re-jailbroke. I've always shown the available memory in the status bar so I could monitor different apps' memory usage. I could usually tell when an app that doesn't manage memory very well was about to crash. Well, after updating to 3.0, and getting rid of all my jailbroken apps except SBSettings and Five Icon Dock, I have much more memory available. Before, I would consistently have between 14-18MB available when Safari was running in the background. Some apps would cause the available memory to go down to 6MB and that is when it is ready to crash. I now consistently have over 30MB of free memory when Safari has only one page loaded in memory. I guess a nice restore/update every once in a while can help recoupe some of the phone's performance.