I know in advance I'm only going to get a pat answer on this, but wanted to express my extreme dissapointment and Discontent here. As Platinum Elite (for whatever its worth ) I travel the US and stay at Marriott properties WEEKLY. I shudder to think of the tens of thousands of dollars spent at Marriott Properties yearly. I went to make reservations today for a long awaited family vacation to Phuket ,Thailand at the JW Marriott or Rennassiance @ Phuket and found that I was only able to book a basic room using my 200,000 + points I have. Not due to not enough points (I have plenty enough banked), but because MARRIOT only allows cash paying customers the benefit of there best rooms at many properties. This is despite the fact that if I was paying cash and was anyone "off the street" the better rooms are available. This is no way to treat your very best customers (those business travellers that keep you in business). It's just wrong, and at this point I am ready to ditch my affiliation with Marriott and move over to Hilton, where this practice does not occur. Furthermore, after speaking with the people at the Platinum Elite reservations line this morning, when asked to speak with a supervisor , I was cut-off TWICE. I'm used to dealing with poor customer service all week long with United Airlines, but I somehow expected more of Marriot.
I have found that upgrades are generally the prerogative of the individual property. I have stayed at some places on points and have been upgraded while at others, I have paid for the room and not been upgraded despite the property being significantly less than full. Your best bet would be to ask, even a few days before arrival, for an upgrade. Nonetheless, you will not know if you have the upgrade until you actually arrive. If there is no upgrade when you check in, ask for it. The worst they can do is say no.
I agree. I have been upgraded to a suite on a points stay. They even threw in the parking for free. While I have not personally experienced it because I have never asked for an upgrade, I have heard stories that customers were denied upgrades at some properties because their room rate was too low. I guess booking room rates on points would be the lowest priority in the eyes of some properties.