I never carry just the wristlet, since I love all my "break-your-back" bags like you. However, they are really convenient for keeping important stuff together in those LARGE bags.
For instance, I keep my id case, coin purse, and cash in the new patchwork wristlet in the pocket on the back of the Lily. Then we I need to get to my stuff I know where it is and don't have to dig in the purse for it. If I have to run out of the house really quickly (like to run for coffee) I can grab that if I know I won't need anything else in my purse.