I tried Hilton as my back up for Marriott recently. Bugs in room (and we are talking a destination resort), over charged room rates (despite my confirmation), bad food and poor service. The kicker was, I never received a response to my letter of complaint. I think Hilton (which now is part of a chain which owns many concepts) grew too big, too fast.

As for upgrades, at Marriott I usually get upgraded to Concierge level, if not I at least get lounge access. And, I only stay about 24 nights a year. They've been good and consistent since 1996 for me.