Ubuntu does much better then networking, wireless drivers are also a big plus. Theres NO WAY someone who connects via a laptop to a wireless connection has a way of typing "sudo apt-get install ndiswrapper" then downloading the windows drivers.... And most (windows) users would rather use the GUI via network manager to connect to a network. Also you can get KDE with Ubuntu with the form of Kubuntu and XFCE via xbuntu. And how is mp3 and dvd not working a cause for panic? Ubuntu takes care of that super easily via codec buddy, you can even get WMA to work! Ubuntu takes care of the things that people don't like/understand about Linux. Software installation is a piece of cake once people remember that Add/remove software actually does what it says rather then in Windows (remind me how to add software from there in windows.,,,?) its easy. Yes Linux needs a good desktop theme but Windows like themes are whats going to have a huge impact in with Vista, people will have to learn a new OS eventually, either they can pay the $300 for the new, bloated, DRMed-to-the-core Microsoft OS, or they can go online or to dell and get a small, fast, easy-to-use free OS. And in the case of Ubuntu most generic hardware works well out of the box.
As for PClinuxOS I have tried the live-cd that came with a Linux Format not too long ago, and I don't really like it that much compared to Ubuntu, besides me not likening KDE much, it just seemed dull, offering not much over my Ubuntu install. But in the end, you can change the theme to whatever you feel like (Currently mine is gnome organized like Windows there is only one bar on the bottom with everything on it, with Mac-OSX controls, metacity top bar and an icon-set that I like the look of but I can't remember the name of)
So yes, Ubuntu is a good public face, good marketing, good security, great stability and insanely easy to use. I can expect it to overcome Windows eventually more then likley when NT7 comes out too soon.