Mass reanimation effects always grab my attention. Interesting variant on
Genesis Wave,
Villainous Wealth, and
Epic Experiment - going from the graveyard instead of from the deck.
As for the card itself.... animating the reanimated cards when X is large is somewhat disappointing for EDH, since it makes them much more vulnerable to removal. It also means you can't use any tap abilities your artifacts may have. On the other hand, board wipes are less relevant in limited and Standard - seems like it could be a potent finisher there, where the 4/4 bodies are more relevant.