I disliked Gnome and KDE enviroments for a very long time, prefering stuff like Fluxbox.
However with Gnome 2.4 and newer versions I have to say that I like Gnome a lot. Most of the time I use the command line for everything, I just use the GUI for stuff that GUI's are better for.
Some configuration tools, window handling, and such. I want to be able to double click on a media file and have it "just work". I like being able to plug in my camera and have it start up ghoto2 right away and stuff like that.
I like the spatial nautilus thing. For Gnome sometimes the browser version of nautilus works out better so I always make sure to have a little filing cabinate thing on the icon bar that runs "nautilus --browser" when I click on it.
Some cool stuff to check out is on you desktop put a jpeg image and a text file. Click on them and see what programs they offer.
Now rename the .jpg image to .txt. Double click on that and see what happens. Then close that out and right click on it, you get the program options for both jpeg and text file.
Then make the file exectable. Get a simple shell script or binary executabe... Name them like a .tiff or a .txt file and double click on them.
Kinda neat how they got it all setup. Much better then the Windows, "Oh, I guess that image.jpg you clicked on was realy a image.jpg.exe and now you have spyware!" stuff.
As for KDE. I don't know, I find it simply irritating. Not that it's bad... Konquerer rocks and all the file managment and abstraction and all that is very nice, but I just can't stand actually having to use KDE for any length of time. Not that I have anything against it, it's just personal taste.