Two rooms upgraded on my stay:

Property: Paris Marriott Opera Ambassador Hotel
Date(s): Feb 24-26
Room booked: Quality Room, King
Room received: Executive Room, King
Elite Level: Ambassador
Award stay: Points
Rate Type: Standard
BRG stay: no
SNAs redeemed: no

Property: Paris Marriott Opera Ambassador Hotel
Date(s): Feb 24-26
Room booked: Superior Room King
Room received: Deluxe Room King
Elite Level: Ambassador
Award stay: No
Rate Type: AAA/CAA
BRG stay: no
SNAs redeemed: no

Comments: This was a last minute booking on Feb 23 for a stay beginning on Feb 24. Within an hour or so of booking both rooms were upgraded. The first room upgrade was substantial, but for the second room, as far as I can tell, the only difference between the Superior and Deluxe rooms is 50sqft.