Playing cards from the top of your library both preserves the cards in your hand for later use and serves as pseudo card draw that digs deeper into your deck so that you can find your bombs
If you win the flip, copy that spell, and you may choose new targets for the copy
The real power is that whenever you gain life, you get to put a +1/+1 counter on each Creature you control
They are printed on an 11 11 sheet with different items appearing different numbers of times
sacrifice decks often go wide, which makes them vulnerable to board wipes, so a synergistic way to get your best cards back has value
Geistcatcher lets you perform disgusting creature loops, and works as a spare piece in countless combos, given you can tuck a creature that can reanimate Geistcatcher under the Geistcatcher