I run Ubuntu/Kubuntu/Xubuntu at home on an old 1Ghz PIII box with 512Mb RAM. It runs just fine. I keep a couple of X-terms open for when I want a command line (fairly often). If I need to be root and don't want to 'sudo' everything I use the common and well-documented workaround - 'sudo passwd root'. Do this once to set a root password and from then on just 'su' the same as on any other xnix system.

Firefox handles my surfing needs, Thunderbird handles my email, OpenOffice gives me MS-Office functionality and file compatibility. Response time is acceptable - and that's with MySQL and Apache running in the background. More RAM would really speed things up but SDRAM is about $60.00/512MB stick and I'm a cheap bastard at heart. :)

The one thing I would recommend is using Xubuntu (Xfce gui) instead of Ubuntu (Gnome gui) or Kubuntu (KDE gui), especially if you have a light-weight video card or not much RAM. Xfce gives you good functionality without the overhead of Gnome or KDE.

Just my .02 worth,

Jack