Desktop
If you are familiar with the Ubuntu desktop on your desktop or laptop computer, let me tell you that nothing will change when you run Ubuntu on a Raspberry Pi board. In fact, if you mostly do home office work (write documents, surf the Web, watch videos, etc.), you can even replace your desktop PC with a Raspberry Pi, which will save you a lot of money on energy bills.
Server
If your more of a Raspberry Pi Tinkerer, then Raspberry Pi Ubuntu server without the included desktop (as long as you are comfortable with the command line) can bring all sorts of benefits.
- Setup a Plex Media server – Serving all your downloaded Videos, Music and other streaming media
- Setup your own KODI server
- Use as backup NAS Storage
- Host your own Website with Apache or NGINX