As always, it depends on what you are doing with the computer. I found this amusing , during the wrap up of the RC5 64 cryptology challenge they made this comment.
"Our peak rate of 270,147,024 kkeys/sec is equivalent to 32,504 800MHz Apple PowerBook G4 laptops or 45,998 2GHz AMD Athlon XP machines."
OSX is still a young unix, Apple is releasing security updates frequently as they find holes. It is very microsoftian in that respect, strange to older Mac users who are used to all that being sorted out decades ago. I tried to remain child-like, all I acheived was childish.