Kubuntu 7.04 Feisty Fawn-alternative installation.
Linux Mint 2.2 Bianca
Of the four tried recently I've found that Kubuntu has the best record for working software, everything I tried work, everything i installed worked, not only did it work it had shortcuts installed in the Application menu so I didn't have to go looking or edit any configuration files to get things going.
PCLinuxOS has the best desktop by far, even beating out Ubuntu, it has a very clean sharp appearance, everything is accessible and the icons are well sized and proportioned. This may sound trivial but when someone works with a machine all day poor desktop design can be very tiring. I have to say that this is a desktop no one would be ashamed to have on their monitor.
Linux mint suffers from very poor desktop design, the resolution starts out way too high to be practical to most people. Even when reset to a size suited to my monitor, 19'', the text is far too small to be read quickly. During the installation it was nearly impossible to follow the text on the panel. The general desktop appearance is somewhat cluttered with many different styles and sizes of icons scattered around.
SimplyMepis suffers from the same poor desktop design that Mint does. I didn't test all the things I wanted to in those distros because I found the desktop too uncomfortable to work with, but later on I plan to check them out more.
I found Zenwalk to be pretty primitive overall and didn't go into it very much.
I'm not into the Pastel Look that seems to have taken over many distros and I think the Linux crews would do well to either get rid of it or at least provide an alternative.
I think if you could combine the sharp desktop design of PCLinuxOS with the functionality of Kubuntu/Ubuntu you would have a very mature and workable OS, just in time to replace win98 and winME on older machines, and compete with XP and Vista on newer ones.