Just using linux, you get to know much more about the way an OS works. Linux admin-ing is a breeze once you get the hang of it (Its a comfort thing. I found it much easier and a lot more intuitive than W2K's hardware wizards); its almost always editing a test-file here- a text file there. No GUI dependency. SUPER SCRIPTABILITY . The oppurtunity to teach yourself admining concepts just looking at the samples and comments ( There are plenty).
And yes! Linux works much better than anything else on older hardware. Linux is pretty stable, a lot more secure than many other offerings around. And did I forget to mention growth? Tell me MS has _actually_ _improved_ their OS in the past 3-4 years? Its basically a mix-and-match scenario. Stability_or_performance_or_HWCompat.
And yes. Games! Game manufacturers aren't exactly ignoring Linux. I get 160+ fps on Q3 and UT on a standard GeFORCE256-32MBSDR/P3733(936)/CUSL2.
Visit freshmeat.net and check out apps there.
Visit slashdot.org and see people bickering there. Sure, it might be disgusting at first, but most of them do have points you know. Lurk around for a month, and post this again after you've tried Linux.
Eye Candy. Your desktop can look much better than you ever imagined. Funnily enough, though this seems like a trvial point, many people I know gave linux a try only after they saw Enlightenment. The transperent shell window is just too much. Can I saw mix that with Ganymade?
And oh yes, try Linux with enthusiasm, and you'll love it. Try it with suspicion, and you'll hate it. Linux is about choice. Linux aims to please. The choice is yours.
Ciao
-khorgath