I am in a state today. Out of necessity, I added a third GB of memory to my MacBook Pro last week because (IMHO) there is a memory issue in Leopard. This screenshot shows what has become the normal state of affairs memory-wise since I upgraded to Leopard.
I may find myself working away with the usual cadre of programs running on my desktop (Mail, Twhirl, iChat, Adium, Preview, Eclipse, iTerm, TextMate) and expect that a fair amount of system resources are being taken up. Fine. However, after shutting everything down I would expect that most of the memory occupied by the running programs is reclaimed by the OS and is available for reuse. That's definitely not the case. WTF is kernel_task doing with a quarter of a GB of memory? Why is Finder holding on to 80 MB?
I have been generally very happy with the Leopard upgrade. Feature-wise, it is an improvement on what was already a fantastically strong platform. However, efficient resource utilization is not an unreasonable expectation for a modern operating system and Leopard totally fails in this area.