I have 58%. I've finished all the missions, I still need to collect all the hidden packages, do all the rampages, buy all the properties (okay, I've done that too), win all the races at the stadium and at Sunshine Autos (I've done/won all the Sunshine races only), rob all the stores, do all the insane jumps, do the pizza, vigilante, taxi, fire truck stuff et cetera to get 100% completion. I can't imagine actually getting all that done, but I'm having fun trying.