You didn't ask about OLCI for hotels. I'm not sure how many chains offer it, and it is in its infancy stages at Hilton, but the concensus on the HH forum is that there is no advantage and actually looks disadvantageous for Diamonds looking for upgrades.

Don't know your rental car affiliation, but Avis offers preferred service. After the first rental, you skip the counter. You either find your name on a board, get dropped off at your car, or use a special counter/kiosk. It can save time if you are happy with the car they picked out for you. No other advantage.