I do almost all of my work now in a command-line shell, including reading email and composing text of all kinds. And I mean it when I say "a" shell---I almost never have two open at once. The reason? It encourages me to use only one tool at a time, which I find makes me more productive by reducing context switching overheads. I don't yet have the willpower to (re-)open Firefox each time I need something on the web, then close it when I'm done, but that's the next step. Who'd have thunk that going back to 1984 would be the right answer in 2010?