Here's the reason it was moved: Fritt's law (google it). It's very easy to 'slam' your mouse to the bottom-right of the screen without even trying: it's impossible to miss the mark. This is also why the Start button is at the bottom-left: you can just slam your mouse that direction and click: you don't have to aim or even try to think about it: it just works.
If they didn't put the Show Desktop button in the right side, it's very hard to click: You have to aim and carefully try to get the pointer at the exact right spot for the tiny little icon (this is how it was in Windows 98, 2000, XP).
I would encourage you to try to get used to it, you'll probably like it after you get used to it.
You can also just use your keyboard: press Windows-D to show the desktop.