I've only had an ambassador for a few months, but she has done exactly what I had hoped for. Though upgrades are cool, I have not asked for them; my real need is for someone to take care of problems so I don't have to waste time on hold or explaining things to less experienced customer service folks.

She's been especially helpful when I've had reservations that could not be managed on line (which often happens with rooms in blocks that are part of an event contract). On a related note, she's run interference for me with some of the harder to deal with Marriotts (Marriott Santa Clara, for example). She can't always get me the answer I want, but she saves me a ton of time getting the answer.

It's easy to get in touch with her. I have her office hours and she usually picks up during those hours. She is also prompt with email replies.

My ambassador is ex Starwood, so she reaches out to Marriott people when there are issues that are complicated and based on legacy Marriott policies (like point prices on reservations booked under the old awards chart that do not yet have a certificate attached).