I could not live without multi-touch now. It is a true mouse killer. I am sure it has added 30% to my productivity alone. Someone turned me on to BetterTouchTools and the rest has been history. With 3 finger click copy, 4 finger click paste I can blaze through a lot of tasks.
Sure it depends on what task I am trying to accomplish, I should have prefaced that. If I am in the IDE I use the keyboard. But, if I am doing tasks like managing files I tend to use the pad.