I think starting small and simple is where it is. If it were up to me, I would do something similar to the “set up triggers for their three favorite applications and use it for a week” but I would take it from the angle of “Name one to five actions you do on your Mac at least three times a day that would make your life easier if you could shorten the time it takes.”

As an example, someone might answer 1) Controlling (play, pause, volume, etc) iTunes 2) Navigating to that one folder where my Downloads go. 3) Adding items to my Backpack account.

Great, let’s implement Quicksilver for those actions and then you’ll see how much time Quicksilver saves. Then, you’ll want to see where it can take you. Like others have said, the only way to “get” Quicksilver is to experience it. Doing so in a small number of ways that are immediately meaningful to the user seems like the surest way to see appreciable benefit from such an ephemeral app. Wei wu wei comes after that.