What problem is actually being solved. You went from having perfectly fine windows machine to having to deal with the fuckery of switching OSes.
When 1 OS does everything and the second OS does most things, and thus you must get the former OS, and it works fine for everything, you might as well stick with it.
The issue is that Windows doesn't do everything:
-Central package management so you you don't have to fuck around with 20 autoupdaters, and updates for every bit of software you have. (I dread fixing family and friends' Windows Boxes)
-Software RAID so a single disk failure doesn't hose your data. (And you get better speed as well)
-Ability to run without a mandatory resource gobbling firewall and virus scanner.
-Ability to run off a CD / DVD / USB Key. (Handy for rescuing other people's shit and your own)
-These days very little fudging with drivers as it will pretty much either work or won't, with the won't getting really rare.
-Settings that are stored in text so they are easily portable. Seriously, if you switch flavours of linux, or install on another computer, you can pretty much replicate the current settings by copying your home directory and the files in /etc you want. This has the added bonus of being manipulated the same way you would with any other (text) file.
-No need to reboot, ever. Reload or re-log, and with things like ksplice you don't even have to reboot a kernel whne updated. (Err, though I do reboot for kernel updates. But I've had home systems stay up for 200ish days.)
-Filesystems that are built around mount points not drives. /home full? Slap another drive in, mount it as /home and copy the files.
-Ability to run on pretty much any computer hardware, with actual software choice.
-Ability to see and modify the code. Even if that doesn't mean much to you it makes for quick bugfixing, and generally better code (on several levels).
-Lots of vitalization, emulation, and remote access options right out of the box.
Would Windows run on this:
http://www.raspberrypi.org/
Yes, that is a $35 computer that can do HD video. (DIY required, and yes I have plans for a few of these...)