I was looking to book a five night stay at a resort in January 2014 and was going to use cash to upgrade the room. While looking at the reward rules under the room type I had selected I noticed the cash rate per night dropped in half in mid January from what it was in early January, but it was January 2013 not January 2014. When I selected the room type using points and cash, clicked on continue and looked at the total cost it didn't reflect the lower cash rate which seems like a huge change from last year, a 100% increase in the cost, WOW! I'll be calling CS to discuss this with them later today, can't wait to see what they have to say about this issue.
Pay close attention to the rules and also the ending cost when booking rooms using this method.