We're going in a few weeks with our first rented points trip.
The major disadvantage is the cancellation policy. Most times it's totally non-refundable. We were OK with that risk given the amount of money we'll be saving.
The other disadvantage is that you don't get daily maid service. Again, for us, that's not a big deal. That's obviously family preference, though. (I am thinking of buying one day of service during our trip, so that's an option if you want it)