hardware autoconfiguration – Ubuntu comes with the drivers for most hardware built-in. Anyone who’s installed a generic version of Windows (i.e., not one pre-configured by a PC vendor to work with certain hardware) knows how nice it is not to have to spend hours hunting around for drivers after installing the operating system.

multiple desktops – virtual desktops are like tabbed web browsing–you don’t realize how extraordinarily useful they are until you try them. There are some third-party tools to achieve the same functionality in Windows, but in my experience few of them work well, if at all, in Vista and above.

software repositories – being able to install thousands of applications from Ubuntu’s repositories in a few clicks is a huge plus. Besides the fact that the software is free and more secure than .exe packages downloaded from random websites, it’s much more convenient to install programs from a centralized location.

ssh client – this probably only matters to geeks, but having an ssh client built into the operating system is a major plus for me. There are some decent ssh clients available for Windows, like Putty, but none are available in Windows out-of-the-box, and even the best of them isn’t as functional as the trusty gnome-terminal.

no antivirus – security practices in the Windows world are profoundly contradictory. Many of the same companies that write Windows software also make millions of dollars selling resource-hogging applications to protect Windows applications from their security flaws. Ubuntu is by no means immune to malware, but practically speaking, it’s as secure as it needs to be for most users out-of-the-box, without any expensive antivirus scanners added on.