As a Marriott Platinum for over a year, with only stays in the USA I can say that the rooms are not that much better, but concierge lounge access is good for the free breakfast in the morning (tho I never get up early enough to eat it).

Otherwise, I do get treated very well. Of course I was treated well when I was Black and Gold and no status, so I've just been lucky I guess. Marriott doesn't have no phone nonsense with 800 numbers, which is a big turnoff for me with the other chains.

Finally, Marriott Rewards customer service is great over the phone (don't bother with email). I've been in only one marginally bad Marriott in over a hundred (including Courtyards and the rest). I've only been in one Hilton and it was a bad experience.

Personally the benefits are primarily bottled water and the 30% bonus points