I'm in agreement with the others responding. As a Diamond, the lounge access and upgrades are almost automatic, and the suite upgrades work - but don't expect them randomly (although they occassionally occur,) I think it's the best, most reliable program - but Starwood is a VERY close runner-up. No experience on #5. Hyatt GP is a great program if you really use their hotels and maintain Diamond status. Unlike some of the others (Hilton,) they really make their program both good for the Hyatt Corp and for the very frequent guest! Highly recommended.