KDE vs. GNOME
My first impressions of KDE and GNOME were recently formed while installing and configuring a RedHat 6.0 system for my Dad. I had tried GNOME out on my own machine around their first major release and didn't really like it; I stuck with WindowMaker. I had never even seen KDE running until yesterday, but I am already quite impressed with it.
At this point, if you don't know what KDE and GNOME are, you should check their web sites: kde.org and gnome.org. The really short answer is that they are each a set of applications which work together to provide the user with a common desktop environment with things like drag and drop and embed-able objects (i.e. similar to things in Windows). They run on various unix systems such as Linux.
GNOME, the newer of the two systems, definitely feels its age, displaying much less polish (and speed) than KDE. While I was playing with GNOME, the panel (like the task bar in Windows) hung up twice and had to be killed and restarted (not an easy task for someone new to unix). After some initial fooling around, one of the first tasks I tried was to get PPP connections up and running. I had a few problems with IRQ conflicts while getting the modem working, after which I went through the (somewhat painful) task of fixing up the PPP connection scripts. Having a way to do this in the GUI would be nice, and GNOME provides a mechanism through their interface to LinuxConf. I've never used LinuxConf before, and the interface I was using in GNOME was "decent" but didn't help me much; I went back to the hand-made scripts. KDE was much easier; I fired up the KPPP program and entered some obvious values into text fields and had a PPP connection with a panel applet and performance graphs in about 15 minutes. Anyone who was set up a Windows Dial-In Networking icon will be right at home.
Next I played around with some of the appearance and GUI options. The thing I liked best about KDE was the font selection; I changed the font in one dialog and all the KDE applications (which I could see) changed. I couldn't find a way to do something similar in GNOME. The default window managers (Enlightenment for GNOME and KWM for KDE) are quite different; Enlightenment is far more flexible in customization of window decorations, while KWM does what it needs to. Window Managers, however, are not carved in stone and both GNOME and KDE allow the options of using a completely different one. KDE's documentation is far more finished that GNOME's; every KDE application I wanted help with had something useful come up when I pressed F1.
Overall, KDE feels far more polished than GNOME and (according to my Dad) is much easier to transition to from a Windows environment. I don't know much about the underlying technologies