As Sandi said, the biggest disadvantage would be the cancellation policy.
DVC availability is a seperate inventory in the computer than the cash inventory, so what you see as available for cash, may or may not be available for DVC.
Renting points CAN save you money over a cash reservation, and you'd need to consider the owners use year, and so forth, as to whether they could even work with you at all on a cancellation, if needed. But if you're willing to give up some flexibility, and this is your first foray into trying out a
DVC Rental, I'd recommend going through a broker on your first rental so you can kind of see how it works, then for future trips, yo can try renting directly from a DVC Owner.
For a bit more info about the process of renting directly from an owner, you may want to read through the
REQUIRED READING thread on the REntal board. It is written mostly for DVC Owners, but as a potential renter, there may be som euseful info on how the DVC System works.