I use gnome 4 because it is the most "out of the way" DE. I disable the dock and use an extension to hide the top bar, so there is literally nothing on my screen but the program(s) I'm using. I haven't found another DE that let's me do that (hiding the dock/taskbar doesnt count, cause it still comes up when you get the mouse too close which is super annoying).

I also like the window presenter thing, which I first started using with KDE. I prefer gnome's implementation though, since it is the same key to bring up the window selector and the app launcher. I often want to switch to a window only to find it isn't open, or I want to open a program that already is open but hidden behind other windows, so it makes sense to put them together. I also can't be bothered to learn more than one hotkey. I've tried to obtain this overall behavior in KDE, but I found it was a whole lot of configuration just to get what gnome already does, so I might as well just use gnome.

I found the "touchscreen-y" interface bothersome at first, but I've gotten used to it. The biggest issue is not showing a large number of app entries efficiently, but it's pretty trivial to remove the entries you don't actually need with alacarte.

Gnome's default apps (like the newish gnome text editor) are getting too simplistic for my preference, but again it's super easy to swap them out.