for me the 2 biggest benefits are non-expiry of miles & being able to use upgrade vouchers on all published fares....

free domestic flight changes & no fee for the citi card are 2 more great benefits....

i also remember an occasion when i was upgraded to first on an international flight due to being plat....a couple of years ago i was flying bom-lhr in première & the flight was so full that they were asking people to give up their seats....when i walked up to the check-in counter the supervisor told me that the only 2 seats left on the flight were in first & he had upgraded 2 plat members to first so that he could free up some space in première....