Avan, if you want to add a single file to an iPod, just go to iTunes > Preferences > Devices > then check the "Disable automatic syncing for iPhones and iPods" box.
After that, it won't automatically sync your device, and you can just add whatever songs you select by dragging and dropping them from your music library to the iPod library.
Anyway, I haven't found any evidence that a Mac is any more locked down than any other system, and I own both a Mac and a Dell with both OSX and Windows. A Mac might require different methods for changing things, but I haven't had any problems with it.
Overall, there's only been 3 programs that I needed that OSX couldn't run, and even then I have Boot-Camp, so my machine can still run them anyway.
I can change the computers theme and add multiple docks and even get Rainmeter-like visuals on OSX.
I don't really think the Mac or OSX is as bad as people like to make it out to be, it's just different and takes a little getting used to; some things are in different places and some things take different methods to do, and because of that people develop the misconception that the system is incapable rather than different.
But, hey, just get whatever computer makes you happier or is easier for you to use.
It's all your choice and preference, after all.
However, it is completely wrong and ignorant to judge people based on what computer they decide to buy. But, that's a different argument altogether.