My experience is the same as refieldmjr's. We always arrange for a towncar transfer, always add a grocery stop, and have used a number of companies. We are a family of three, and all three of us go into the grocery store and leave the driver in charge of our luggage. Of course I take my purse and my DH takes his wallet, so we never leave cash/credit cards, etc. in the towncar. We have never had concerns that our driver would drive off with our stuff, and really I don't think the incentive would there be for drivers to do so. Most people just take a bunch of clothes (that fit them and not the driver) and personal items to WDW. So, if the driver drove off they would end up with a bunch of stuff that probably wouldn't fit them, that they would only get garage sale value if they tried to sell, and they would likely lose their job on top of it.