First experience using FHR booking via Amex... went perfectly (as far as I could tell):

Booked Deluxe Guest Room for $279/night

All FHR amenities explained at check-in, was also given 2 letters (one from Hotel, one from "Amex") explaining benefits.

~ Upgraded (one-level) to Superior Room (359/night)
~ Breakfast for 2 (up to $40) - we wound up charging about $60 to Room Service for Breakfast, but it was all taken off without asking.
~ Late Checkout
~ $85 F&B credit (applied with no problem to our room service dinner)