I also see a lot of PayPal orders dropping out. They pay in PayPal, but the order shows up as "Awaiting Payment" in Smith Cart. I will change my PayPal merchant account and add the "Auto Return" option.
BTW as of 21 Apr 2012, to get to the PayPal Web page options, the path is:
MyAccount -> Profile -> My Selling Tools -> Website preferences (under "Selling online") -> Update -> Auto Return