Recs.
Updated
SpecsUpdate
Pros
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 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.
Cons
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.
Con Tends to do its own thing
Ubuntu has a user interface that is specific to Ubuntu and is now working on its own display server. It also tends to have configuration that is done slightly different (and arguably more beginner friendly) than elsewhere.
So while this is a great Linux distribution in its own right, it might not be the first choice for someone wanting to learn Linux itself.
Con Relatively high system requirements
The default GNOME desktop environment is a resource hog which requires hardware accelerated graphics rendering in order to run smoothly, making out of the box Ubuntu unsuitable for low end systems and older hardware. Even mildly aged hardware, you'll get far better performance out of a lighter desktop environment like LXDE or XFCE.
Recommendations
Comments
Flagged Pros + Cons
Con Unstable
Some people pointed out that updating Arch is a high risk affair. And one should carefully read forums before doing it. The same is true about Ubuntu. Making system updates (like it was with 10.04 to 11.04) that screw so many things up became a routine. Even LTS releases should not give confidence that it will work.
Pro Great long term support release schedule (2 years)
This allows for users to always have a new supported release available without long unkown wait times in between.