Kubuntu

This distribution has KDE as it's default desktop.

With a bit of configuration, it can be used by Windows or Macintosh users with very little training.

It has a large community providing help to people who like to customize behavior.

Debian package system and core work

with some good direction from http://ubuntu.com which helps direct development of "Linux for Human Beings"

and KDE which is an actual usable shell ( user interaction layer)

Since the default desktop on Ubuntu, Disjointity, (They call it Unity) is unfriendly and onerous, very few people recommend using Ubuntu. We would rather use kubuntu, and have used xubuntu and lubuntu with some people preferring Mint