As the only free monkey, the Dart Monkey is effective in the early-game for defending attacks without spending gold. Despite this, it also takes up a deck slot that could be better used for other cheap defensive cards, such as the Dart Monkey Twins or Barrel of Monkeys, so it is not recommended in many decks. However, it is still helpful in aggro for heroes without defensive abilities.
Dart Monkey notably has more damage than a Monkey from Barrel of Monkeys, making it slightly better if the deck it is in wants to spend as little money as possible on defending.