A nearly non existant benefit. I have been Plat for 2 years and now Diamond for the last 3. I recieved 1 upgrade from a standard room to a full suite for a 3 day stay 2 years ago. I do notice a notation on most of my res at the front desk about the upgrade. But, in practice they never upgrade you.If asked they will usually plead ignorance about the whole benefit. I called corp once on this. They told me since most BW are privately owned there is nothing they can do about the lack of upgrades.
Mildly annoying benefit, essentially useless, just hot air pr IMHO.