For me it`s the 100% protection against viruses and atleast 10 times(guesstimate) less crash prone than XP are the biggest plus points for Mac.
I have a MB for all my desktop and portable needs. But I love movies and TV shows, so decided to built an HTPC and connect it to my TV(Apple TV seemed a little underpowered and feature less. I still regret it). I bought it in Feb 07. After 15+ reinstalls of XP-MCE and Vista Premium its still not working. I follow every guide from Google, follow the instructions to the T and after 10s of manhours once I get it up and running (with the ability to play mp4 and mov files in MCE) it dies on me for no reason whatsoever. It was working five minutes ago. I didnt do anything. Still it wont play that same file which it played just a little while ago. Restarting cured the problem 50% of the times. Otherwise resart, restart, then reinstall, restart, format, reinstall, restart...........
Now I`ve lost all hope and use a keyboard and mouse with my HTPC to run whatever I want in VLC only. I dont even connect it to the internet. Once I did to make sure all the critical updates are installed, Next thing I knew there were two trojan horses on my PC. I didnt even open any web browser. Not exactly the experience I hoped for.
And here is my MB. It`s been almost 20 months since I started using it. No need for any reinstalls yet. I restart it maybe once a week(that too mostly when update requires me to restart). Everything works as it used to 20 months ago.
In short you can sum it up as "It just works"
Now as far as quality of hardware is concerned I dont think Apple has any real edge. It`s as good as any other brand. With millions of Macs selling every year you just cant expect Apple to be 100% perfect. But once you add OSX to the package, there`s no better deal anywhere. Just make sure you get the Applecare for the MBP. You`ll need it. My MB is going tomarrow for a Fan and SuperDrive replacement. Without Apple care I`d be doomed.