The London Marriott's are reimbursed a little over $200 a night from what I could tell for my reward reservation there. Pretty low for their regular rates, but still not chump change.

As a plat, I did get to concierge level about 90% of the time, suites about 5% of the time, and no noticeable upgrade about the rest of the time. Which is why I left for Starwood..