This was one of the basises for my rant on the other thread. I found this out on the old macs, but I stood corrected the newer mac osx versions were far superior than anything before it. One of my main curiosities is to see how advanced you can delve into it.
Re: how far you can delve into it.
OSX.5 Leopard is a fully certified UNIX which means you can delve into as far as you want with the fully functional Terminal (think Command Line)
Anything you can do with Linux or Unix can be done on a Mac.
On an Intel Mac you can also do anything you can do with any version of Windows for computers.