That means when you next cast a spell that turn, you get to exile cards from the top of your library until you exile an instant or sorcery that costs less than the original one and then cast it for free
With cards that move counters around like Scholar of New Horizons or Goldberry, River-Daughter, you could even speed things up for a faster extra turn
Merry rewards artifact production with 1/1 lifelink tokens, which all of your token doublers interact with and the lifelink on those tokens assists with your life gain synergies
While providing your opponents with mana sources comparable to treasures may seem counter-intuitive, whenever an artifact an opponent controls is put into a graveyard (such as when they sacrifice a Banana), each Ape and Monkey you control gains a +1/+1 counter, meaning your opponents' treasures can cause your creatures to grow to massive sizes
Alternatively, pack in a suite of second and third card draw payoffs like Morska, Undersea Sleuth