If I had to pick one way that my Filo paid for itself more often than any other, it would be as a keeper of directions and other place-related details. When I get directions to, say, a friend's house, I write them on a single page. I can move the page around, edit it, and move it from one organizer to another without rewriting it. And no matter how much time elapses, years even, I'm always able to return to that same address (assuming that my friend hasn't moved). Need a code to get into my doctor's office door? It's right there on the same page.
Similarly, whenever I call a phone number, I write it in the Filo, even if I don't know if I'll ever need it again. I did the same thing on my Palm. If I ever wanted to order a pizza from the same place again, I could do so without looking up the same number more than once. For some reason, that efficiency really appeals to me. Look a number up once, write it down once, use it forever with no further effort.
But then, I'm weird.