I have both: mini pochette in the Trunks & Bags version and the Mono pochette. I actually do not use my pochette very much but I would always keep it because it can be used as a small accessory bag inside a larger purse.
However, I use my mini pochette all of the time!!! I keep receipts, cards, coupons, stamps, a Palm PDA, and other misc. things inside of the mini pochette, so I find it very useful!!!