I've been stating at a Renaissance for 3 or 4 nights a week for the past 4 months and haven't been upgraded to a suite. Every time I check in I ask if any are available. With the exception of 2 times, a suite has been available. Last week, when I checked in, the clerk informed me that suites are available starting at $350 a night. I responded "Not for a platinum guest requesting an upgrade." He put me in an executive king on the concierge floor.
Two colleagues of mine have been staying at a Hyatt in town for as long as I have been at the Renaissance (they are diamond). THis week one is in the Presedential Suite and the other has a huge double suite.
I'm just frustrated with Marriott's treatment of elites in general. If I wasn't a slave to the points, I'd switch.