Way back when, the first combo I built a deck around was Force of Nature with a Spirit Link on it. If, at the beginning of my upkeep, I have less than 8 life and I don't pay the upkeep, will I lose the game before the life gain kicks in?
When the Force of Nature damages you, Spirit Link's trigger goes on the stack. If, between sustaining the damage and getting 8 life back from Link, your life total hits 0, you'll die.
This is confirmed by the Oracle text for Spirit Link:
Luckily, you can avoid this problem by replacing Spirit Link with Lifelink.