Clearing the Desktop
The most useful aspect of Aero Peek is its desktop peek feature. If you want to take a quick look at the desktop without hiding all of your windows, simply move your mouse pointer to the lower-right corner of the taskbar; at once, all windows will turn transparent. Click the lower-right corner of the taskbar to hide all open windows and see the desktop; click again to get back to work. This option is roughly equivalent to the Show Desktop feature in OS X's Exposé, which moves all windows off your screen with a keystroke (or with a flick of the mouse, if you have set a hot-corner for Exposé).
Both Windows 7 and Snow Leopard are solid updates to their respective operating systems, but I can't say that either one will persuade many users of the competing OS to cross to the other side. If you're perfectly happy with Windows, Snow Leopard probably won't make you lust for a Mac. Likewise, if you're a Mac user and weren't considering switching to Windows before, Windows 7 is unlikely to change your mind.