The most popular Linux distribution, Ubuntu offers different OS versions for various devices like desktops, servers, tablets and phones. The desktop version, a fork of Debian, is very stable, particularly due to the number of active users, and provides a lot of features out of the box, so you can start working without having to install hundreds of drivers, tools and software first. For a lot of people, Ubuntu is the most competitive free OS to Windows and Mac.
Pro Dedicated software center
The Ubuntu Software Center offers a GUI interface for installing new apps which is extremely easy and welcoming for beginners to Linux. But it should not be used by more advanced users since the method of installing through the terminal is much faster and easier after one is used to it.
Pro Just works out of the box
Lots of support for hardware, lots of pre-installed software, and a smooth install process means less time downloading drivers, less time digging through configuration files, and less time deciding on software to use just to get up and running. It also means less time digging through forums looking for support.
Pro Use it on almost any device
Not just for laptops - Ubuntu was designed with tablets and touchscreen devices in mind, and with phone support on the way. Ubuntu also has Long Term Support releases, as well as a version oriented toward servers, so you can use the same OS at work or on mobile as you do on your desktop.
Con Canonical does not respect Ubuntu users' preferences
In 2012 it became impossible in Ubuntu to move the close-window-button back to the upper-right corner of the window, where it always was before. To the questions of their users Canonical replied that they know better than users where it would be convenient for users to have the close-window-button.