I find that Diamond Ambassador helps with special requests - for instance, I've traveled with some of my in-laws in Vietnam and been able to request upgrades, breakfast or lounge access as a courtesy on a second room. I'd never expect that in the US of course, but it seems like a good springboard for making asks like that.

Our checkout at the IC Halong Bay was smooth and all the Chase+Ambassador credits posted automatically, and our 16:00 late checkout was also honored proactively without needing to request it. Looking back at our upgrade, the two-bedroom residence we ended up in is technically on the list of excluded room types for Ambassador upgrades, so maybe it's fair to say that the Chase upgrade was helpful in securing it? Hard to say for sure, but good odds we'll be back in the future, as the property is really competitively priced for the quality - particularly if you have lounge access.