Microsoft Windows 7 Professional

Ease of Use: Due to the familiarity of Windows OSes, as well as the intuitive start menu and taskbar, Windows 7 is very easy to use for novices and power users alike. The Plug N' Play feature which automatically installs the driver of a plugged in device is an example of how intuitive the OS is.

Speed: Windows 7 is a very fast operating system, and huge improvement over Vista. Through maintaining the system's hard discs and registry, I've not noticed any speed changes since the first install of the Windows.

Stability: The stability of Windows 7 is great, and I've never had issues with it.

Ecosystem: Being compatible with previous programs released on older re-incarnations of Windows, as well as having the support of Microsoft have resulted in Windows 7 having a very rich ecosystem of professional and productivity apps, as well as games. W7 is also compatible with a huge range of hardware. Indeed the ecosystem of Windows is unsurpassed, and unchallenged in the computer world.

Configurability: Windows 7 is definitely configurable and can be changed and adjusted up to a good point. However, this does not even come close to the versatility of some Linux distros.

It's a great OS, I got it at launch, and it's still an absolute pleasure to use.