This is the beauty of Food tokens: they need not activate the lifegain ability to count as being sacrificed
The first are the many Angel token makers that have seen play in Standard and Commander
Azusa combines nicely with card draw, cards that let you play lands from your graveyard, landfall, and of course, gigantic green creatures or eldrazi
Efficient removal continues to be stapled onto Constructed decklists
However, the last part of the ability will check how much life you've gained as the ability resolves, so if you've only gained 5 life this turn by the time the end step comes around, you could still gain 2 more life while this ability is on the stack in order to return the target creature card to the battlefield instead of your hand
The service remains at the same rate