4PM checkout really is the best best, both for work and pleasure.
I love being able to change and use a non-public restroom before catching a flight. Or if you have to book a later flight and have some dead time it means you have somewhere to work/veg out that isn't a Starbucks or something.

I have to go to a lot of small places in the US and Marriott/SPG really has the best coverage in the US outside of large cities.