There's a tradition in the Lovecraft Mythos that nightgaunts, frightening monsters that they are, are at times helpful and benevolent. Keeping with that tradition, under the right circumstances, this encounter is a godsend. How's that? At a modest fare of 1 damage and 1 horror, the "Nightgaunt Express" (as my group has come to call it) offers two very valuable services:
1) Saving you actions if you need to move across town. I don't know about you, but out of every action you can take on your turn, Move is my least favorite. It's slow, it does nothing on its own, and depending on the board state, moving toward a location often means moving away from a location you'll need to go to later, costing you even more actions. There's a reason cards like Shortcut, Elusive, and (sometimes) Astral Travel are so highly valued. Actions are precious--far more precious than the health and sanity you lose from failing the test for this encounter. Actions you don't need to spend moving can be spent gathering clues, doing damage to enemies, playing cards, and completing Act objectives. Why walk when you can fly?
2) Rescuing you from danger. This is a fantastic encounter to draw for investigators who are waylaid by (non-Nightgaunt) enemies and are either ill-prepared to fight/evade or whose actions are better spent on other things--seekers mainly, but anyone who just doesn't have the right cards in hand or in play can appreciate a helping claw from our favorite blank-faced tickle monsters.
About the third or fourth time my group drew this during our first playthrough of the Midnight Masks, we learned to love it. It allowed us to budget our actions to do just enough damage to take down a very tough enemy at a crucial moment. It reminded us of the many, many times--playing the 2nd edition of the board game--nightgaunts helped our investigators get across town and past tough monsters on their way to explore a gate. All aboard the Nightgaunt Express!