I have about 4 of the things sitting in a cupboard at home. I can report that one was recently used for the safe transportation of some Yankee Candles on a recent flight. No shoes though GJ, sorry [:#]
In the past I have used the old Econ/PE bags as shoe bags but on my last two trips I used the new UC ones and loved them. They're less bulky than the plastic bags
The plastic Economy ones are very useful for transporting kids stuff, the PE (purple) ones are a complete waste of space, and the UC shoe bags are very handy for putting ones shoes in the suitcase and stopping my clothes from being soiled.
They are particularly useful when the Security folks at IAD regularly unpack and attempt at packing my stuff when I fly via Washington.