I haven't been assigned a personal concierge, and quite frankly I'm not even quite sure that that benefit truly exists. I've called the Platinum line for all my upgrade and special requests and guess what? I'm batting 1000. If I haven't been convinced that the current concierge has at least tried to accomodate my reasonable requests, I just call back and try again with a different one. While it is certainly true that the hotel always has final say, a request can't be granted if it isn't forwarded to the proper hotel contact. Most often the concierge will put me on hold while they call the hotel directly and do their own form of negotiation. Thusfar I've been guaranteed a suite on roughly half of my stays well before the check in date. When the hotel is a little more tightfisted and won't commit a suite for the price of a regular room beforehand, I'm usually happily surprised at the front desk. You can't fault the hotel for attempting to sell its inventory at a price commensurate with its value, and some hotels have a much smaller inventory of suites available. Capacity controls exist at hotels as well as airlines.