It makes life so much simpler especially if you have a widescreen monitor or a multi monitor setup. Just grab a window and throw it (not literally) to the top to maximize it. Pull it down and it will restore to original size again. Drag it to one side and it will tile to fill half the screen real estate. Dragging it to another monitor also becomes easy as it does not lose its state. It is very intuitive and soon becomes second nature when comparing two documents, copying or moving files between two windows, maximizing the window you’re currently working on, or expanding long documents so they’re easier to read and require less scrolling. On tablets, you can just swish your finger to the top to maximize. Probably not all that usefull but an indication of the things to come in future UIs.
Just in case you find this feature distracting, remember that it can be easily disabled. Run REGEDIT from the Run Command dialog box, go to HKEY_CURRENT_USER\Control Panel\Desktop, set WindowArrangementActive to 0, and reboot. Now your windows will behave just as they always did.