When these types of rates first started to appear a few yeard ago, I too found inconsistency in whether my credit card was actually charged before my arrival at the property.
But within the last year or so, there has been 100% consistency - the room and tax amount is ALWAYS charged to the credit card a few days after the reservation is made.
As an example, I just went back and checked my records for my last prepaid stay, for a hotel in Detroit:
Reservation made: August 4 2003
Credit Card charged: August 6 2003
Stay: August 20, 2003 (checked out on August 21)
Meal/Incidental amount charged to credit card: August 23, 2003
[This message has been edited by Non-NonRev (edited Jan 11, 2004).]