After succsessfull update to 10.5.2 i was surprised at the less RAM usage. I have 4096 MB RAM, bevor update the o 10.5.2 the RAM usage was very High after Reboot 850-950MB without any open application. Skype use 220MB, and my 4GB RAM vanish fast to 150MB Free RAM after couple houre. Now since 10.5.2 a fresh Booted System just 550-600MB need of RAM, after couple houre work and open Application i have 1.8GB Free RAM. I am Positive Surprised.