MEPIS is really good. I've been using it off and on for years (using it right now on my Dell Latitude laptop). But it's not a build of Ubuntu; it was around long before Ubuntu ever showed up.
Actually, up to 4.3 was a debian etch build. Warren began using UBUNTU on version 6.0. It is an EXELLENT distro. I am always the evangelist for it, and am thrilled you like it too!