The problem with using a pocket-size Filo as your wallet (if you're a woman, as I am, and don't wear trousers with big honkin' pockets): there's no coin purse. Yeah, yeah, some models have a zippered pocket at the back, but I don't want to put change in there. It would make a big, ugly lump and distort the leather. I use the zippered pocket for a emergency piece of folding money and a couple of loose checks (so I don't have to carry a checkbook).
So I'm forced to carry a separate little change purse, as well as a card case for the cards that don't fit (and that I don't want) in my Filo's card slots (library cards, discount cards to stores I shop at maybe once a year, that type of thing). It's not as bad as it sounds. I keep those two tiny peripherals in a compartment of my handbag and only end up reaching into it about once a day. Everything I need to make a purchase is in my pocket Filo 99 percent of the time. If I want to travel light, I can take my pocket Filo and cell phone and leave the rest of the handbag at home.
Then I saw this: Always have correct change in your wallet
If you don't feel like clicking the link, it shows you how to make a card with coin slots that hold the minimum number of coins you need to make any amount of change from 1-99 cents (3 quarters, one dime, 2 nickels, 4 pennies). How cool would it be to have one of those, in plastic, with holes for the Filofax rings? It would fit into the organizer just like that post-it thingy. Then I realized you don't even need that. If you really only have to carry no more than 10 coins, maybe keeping them in the zippered pocket, or one of those plastic zippered pouches that go on the rings, wouldn't be so bad after all.