Didn't see 1 big reason mentioned - Live cd's !!
Whether its system rescue,, tv recording (myth), htpc (xbmc) or a million other specialized use cases, you can find a Linux live cd for it. And they fit on a usb, boot and run faster than Windows. I'd never use Linux for a desktop os (no need really and it'd take me 3x to get stuff done as I'm not familiar) but there are plenty of Linux distro's I use.
Another reason - the regular flame wars over Linux are almost always informative
Have to go with that. Stuff like Macrium Reflect uses Linux boot/restore CD among other options. The coolest thing though, was creating a boot diskette that booted your HD install. Like say your MBR got hosed and you didn't come up to the usual boot menu, stick in the diskette and boot from it. It mounted the HD Linux install as root after booting. In fact you can do a similar thing with a USB key and Windows if you have a machine that can boot from USB and bootable USB key drives. You boot the UBS key and get the same boot menu you would if the system booted from the HD(the multi-boot menu on a multi-OS machine, not the repair install jazz.) Like the Linux diskette, it's dedicated to the machine you made it with.

















, Compiz eye-candy, and Unity (i.e. Mark Shuttleworth's new 'girlfriend') what exactly is it Linux is "supposed" to look like?

It can look like anything it wants to, except Mac ... That's been done (it sucks) and folks need proper alternatives.