This is extremely last minute, but don't forget that changes to the Marriott hotel categories takes place on March 15, 2012. Today is the last day to book reward nights at the old rate. If you haven't already yet, take a look at the official list of all hotels that will have a category change tomorrow. This is especially urgent for those who have free nights that were earned via the Chase Marriott Rewards Visa or through the MegaBonus promotion. Those free nights are only good for Category 1-4 hotels. Since 96 hotels are rising from Category 4 to Category 5, make sure you redeem those certificates by tomorrow!
If you have a current reservation for a hotel that is moving down a category, you can receive a points rebate after the changes take place. According to Marriott Rewards, 3% of their hotels are decreasing by one category (100 hotels), while 15% are increasing by one category (526 hotels). Burn those points at the lower redemption rate while you still can!