So now that you are here -
Can we get the official what should happen and what should we do answer to Elite Upgrades.

1) What does the phrase "Finest Available Accommodations" mean?

2) To be more specific - What should I expect to receive for an upgrade when I check-in to a:
a) Marriott
b) Courtyard

3) If I check the computer and it shows availability of a certain room type but when I check-in the front desk says there is no upgrade available - what should I do?

4) Just my personal opinion -
I do not consider concierge floor as an upgrade - I get access to the lounge so being on the same floor is not a great benefit.