The security and quality of Mac OS X with the versatility of also being able
to run certain Windows ONLY applications and games natively under Bootcamp.
Connectivity with USB 2.0, F/W 400, 800, Toslink and mini jacks for audio I/O
Mac OS X Pro applications for audio, video, graphics, scientific and every possible office requirement.
As mentioned above there are ZERO effective viruses and less than a handful of proof of concept vulnerabilties that can in any way harm your system with reasonable and responsible care.
Running Mac OS X allows you worry free operation, letting you concentrate on getting things done.
If you simply must run any Windows applications, it's best if you do so
offline or only when connected to a known secure server.
Otherwise, you would still need to protect your Windows partition as with any Windows machine.
Mac OS X gives you complete control of your system once you know where
everything goes.
For shared systems, you have complete control over what other users
may or may not do in any secondary non administrative accounts.
You can limit access to each individual application as desired.
With iSight and iChat A/V you also have the capability to video conference
or create your own video podcasts.
With Keynote, your presentations will command the floor above any Powerpoint presentation.
What's not to like?
It just works!!!!