Recs.
Updated
Specs
Pros
Cons
Con Rubbish UX
The start button is right next to the windows button, so when you want to click the unity start button, you often end up closing an application, or clicking the browser back button because those buttons are just pixels away from the start button. Therefore, the UX/UI is very very poorly designed.
Con Dead
Canonical has ceased the development of the Unity desktop environment, along with the Mir display server. Future versions of Ubuntu will be shipping with Gnome 3. While branches of these are likely going to be maintained by the community, it's difficult to say how strongly these will last considering they were designed specifically for Ubuntu, they had never reached stable release, and more popular alternatives are already present (Wayland in the case of Mir).