When it comes to desk top environments I'm flighty (like all blondes should be) All of them have their advantages and disadvantages and I am still waiting for the perfect one to come along (roll on the release of e17!)
Here is some info on the desktop environments I have used to help you in selecting your graphical interface and some hints and tips for getting the most out of them.
Enlightenment is my favourite. It is truely the most beautiful and has the most customisable desktop. e17 is still under heavy development so there are issues with getting things to work at times and it frustrates me beyond belief when I update and my beautifully set up config is lost once more (saving configs will apparently be one of the things which will become available once they have finally agreed and stuck with an underlying structure). Then, of coarse, there is the fabulous eSheep !
KDE is apparently great for developers. Not really being one of those strange nocturnal creatures some of its advantages are lost on me. It is however the desktop I'm using most often at the moment as it seems to have the best of all worlds - not as reliable as gnome with ubuntu but more static than e17 and not as customisable as e17 but more easily customised than gnome.
Ubuntu and gnome work very well together. It has some great features, particularly when using external devices, and is very slick. However I have some major issues with the lack of basic desktop features. I have multiple desktops set up with brightside (which frequently crashes) but I can't get it to remember where my windows should be when I start up (I like to have my mail client and gaim start when I start up and want to have them on different desktops - not much to ask you would think) Unfortunately after chatting on the gnome help pages they admitted that it is not actually something gnome can do, nor is it one of their priorities. It can remember some window locations, such as firefox, but evolution and gaim are no go areas.