KDE and GNOME are both desktop environments, comparable in some ways, but vastly
different. I disagree with a previous comment that KDE is like Windows. The only
thing that is the same about KDE and Windows is the panel is at the bottom. The
difference stops there.

I could say that GNOME is like Windows because it used double click. That is a
simplistic view of GNOME and it is equally simplistic to say KDE is like
Windows. BTW, KDE uses single click.

The big difference between KDE and GNOME is that KDE is more unified and
configurable. It has a control panel and you can change all of the settings from
there, even get desktop effects without installing Compiz. It is more unified
because the applications that come with it are made to work together. Akregator
is the RSS feed reader, but you can get many of the same features with Kmail,
and even transfer settings. Kontact similarly works with Kmail. With GNOME
things are more disjointed, but things still work well. Pound for pound you get
the same things in GNOME, but the look and feel is not the same.

KDE has all of the bells and whistles and GNOME is more basic. KDE 4 is written
in QT4 which is an update of QT3, but GNOME is still written in GTK that has
been around for over a decade. GNOME looks a little dog eared IMO. KDE 4 has
plasma and desktop widgets built in. It looks very new and current. (If this
makes it like Windows 7 then GNOME is like Windows 98.) Despite all of these
capabilities KDE and GNOME run about the same speed.

Do not run any KDE below 4.2. KDE 4 was very buggy and lacked features when it
first came out. If you are using Kubuntu 8.04 or 8.10 then don't bother with KDE
for this reason. If you install Kubuntu 9.04, the latest version, then you will
be running KDE 4.2 which is okay, but not as good as KDE 4.3, the latest
version. You can get KDE 4.3 after installing by changing your sources list in
Synaptic.

I like GNOME and KDE. I use them both for variety, but prefer KDE due to its
power and features. My only problem with GNOME is the inclusion of Mono (F-spot,
GNOME-Do and more). Mono is an open source implementation of .NET and its status
is unclear and it is dividing the open source community, much to Microsoft's
delight which is why they stay quiet on the issue. I just wish that it would go
away for that reason. I don't have anything against it except what it is doing
to us. KDE is Mono-less. I will now firmly grab hold of my tongue....