Not bad if you've got a sac deck going. It basically reads "every creature you sacrifice triggers Grave Pact twice". On its own, it's not that great (all it does is replaces itself with a gribbly), but it can allow for nice combos/more devastating combos. I'm not going to complain about it saying "nontoken creature" since that would make this degenerate. In fact, the only thing I'm going to say is a downside is that it's a 2/2 for 3, which isn't great on its own.
Pros: Replaces your dead dudes
Cons: 2/2 for 3, replacements are gribblies