Dows - > Ubuntu

I've been a Windows user for a while, but now that Ubuntu came out, I decided to try and make the switch to 'nix.

Is Ubuntu all that it's cracked up to be? And will I be able to learn the nix commands so I can eventually switch over to something along the lines of slackware?

I've heard some say Kubuntu is better because of KDE. Is there a big diff. between ubuntu and kubuntu?