Windows 7

Although Windows 7 has a good UI, but it's buggy and commercial. I think Ubuntu is much better.

I used to like Windows but after some time using it, I'm starting to hate it because

1)cannot completely remove Internet Explorer,Windows Media Player,Paint,etc which takes some space in my small hard drive

2)too many maintenance and apps needed to optimize Windows 7

3)a pain to find driver after clean install

In my opinion,Ubuntu is better than Windows 7 (never tried Mac yet)

I love Aero Snap (it's especially fantastic with two monitors). Just pull down on your browser's taskbar, and woosh! The window is no longer maximized. Holy crap! It gets even better if you're using a modern browser, which allows you to drag-and-drop individual tabs. Combine this with Aero Snap, and pretty soon you're flipping windows all over the place. Wooooooooooo! Want to see your desktop? No problem, just drag that maximized window out of the way. Sick of your stupid desktop? Drag the window back up. Maybe you want to see two windows at once-- no problem. Just flick one window to the left of your screen, and one to the right. Screw keyboard shortcuts, you have a MOUSE! With Aero Snap in Windows 7, window management is simply super special awesome.

Although Windows 7 does have (decent) backup capabilities it should not be tagged "backup".

Short guide to make this OS leightning-fast: disable useless services, disable visual styles, install xplorer2 for file management and bbClean shell.

I used the demo awhile back and its a great OS. I look forward to upgrading to it for my next computer

Unlike Vista, which only introduced pretty colors and pretty annoying UAC, Windows 7 is clearly better than its predecessor (though the bar may have been set a bit low). UAC can be toned down instead of just plain shut off, though I still prefer to turn it off completely. The new taskbar is a massive improvement of the traditional taskbar of the Windows OS. And there are lots of other cool stuff, too.