I stay at Marriott's primarily for two reasons:
1) They are usually consistent and I usually know what to expect from the brand chosen. Not perfect of course but much better than some others.
2) When things don't go well it is usually resolved to my satisfaction in the end.

I'm not a chronic complainer but I've found that hotel and Marriott management are empowered to make the customer happy in the end. This has proven true on both paid and reward stays. I'm not very picky on business trips but family vacations are another story. This is opposed to a problem with a Hilton Reward stay where they really couldn't give a dam in the end that the hotel turned out to be a dump. I have yet to contact Marriott with an issue that wasn't ultimately resolved.

I'm in agreement with megtravels that the hotels should consider that customers spend thousands of $$ in their hotels accumulating enough points for a reward stay and don't want to overlook a dumpster on the family vacation if there are better rooms available. I know points reserve a garden view or other basic room but taking care of the customer on a reward stay keeps the cycle going and the hotel chain will continue to get their business.