The most compelling functionality of Linux over Windows, by far, is virtual desktop support. (For those unfamilar on the concept, it’s the ability to create multiple desktops with different windows on each.) When in Linux, I can keep separate desktops dedicated to e-mail, web surfing, and programming, and switch between them immediately.
Window managers for the Linux-based Gnome and KDE display thumbnails of the desktops, let you drag windows across desktops, and allow you to switch between desktops using either hotkeys or by moving the mouse across screen borders. As it turns out, only one of the 20+ third-party Windows utilities supports all of these features: Enable Virtual Desktop. Try to ignore the awful web design, and just download it. It costs $19.95 to register, but it’s worth it if you’re a Linux expatriate.