I've been very happy with i3wm since I started using it, but I suppose it probably doesn't qualify as a desktop environment. I like the flexible keyboard-driven layouting and vim-like keybindings, and dmenu gives random access to any application without the need for menus or the like. I don't like the interruption of having to reach for the mouse. Combined with vim, tmux and Pentadactyl (a vim shell for Firefox), I get a setup where I rarely need to take my hand off the keyboard. If I were to choose a setup to stick with forever, this would be it.
