Two additional janky situations:

• Have Open Gates in two characters. Then the card does not only skip backtracking, but let's you skip parts of the map. Some copies might be useless, though.
• Play an Open Gate with "You owe me one" from the hand of your friendly neighborhood mystic. You can do this from the other side of the map. Sure, it's not fast anymore, but enables you to reunite your party. Played this in Lost in Time and Space to pull the Akachi of the team to the top as Mandy.

Not terrible, not great. Good for very specific characters, anybody else just doesn't have the deckspace.

Open Gate is fun, whatever else it may be. Opening a gate to create shortcuts is fun, when you pull it off usefully it's a YAY moment!

• That time where you create a short shortcut to cut through an annoying spot repeatedly (1st Scenario of Carcosa comes to mind).
• That time when you set up an initial gate and create another gate wherever you happen to wind up at during the scenario to escape back to the startpoint through (2nd Forgotten age for example).
• Some maps have you running back and forth in general and setting up a major network node speeds your back and forth moves greatly (2nd Core).

The thing about this card though....

You tend to play this card in places where you HAVE been, and it wont help you get places you're actually going to. The only times this is helpful is when you backtrack for some reason or if a map isn't ushering you in just the one general direction (which most maps have a tendency to do), in many maps you're only netting one action saved, sometimes two, depressingly often zero.

In multiplayer it's WAY more helpful, one character can pepper locations like Hanzel & Gretel and the other dudes skip-step in their wake. Going faster than them other characters is needed for this to be possible, it's not unusual for a character to surge forward to get clues or an enemy, you can plan rounds where a vanguard is dropping gates and the others follow suit to catch up. You can easily save your team half a dozen+ actions in this way, even if you never actually used the gates yourself.

Synergies for Open Gates include:

• and movement cards. Shortcut, Elusive, Pathfinder, Think on Your Feet all help you move faster, covering more ground (and staying ahead of your friends) helps set up good gate spots. There's also Astral Travel and Mists of R'lyeh, the latter in particular will find you spots to place gates in a jiffy. Also Arcane Initiate really helps you set up a network that much faster.
• Luke Robinson is all but printed for Open Gate, or vice versa, you'll often be in the circumstance where he can pick 2 viable locations to go, place a gate on one, investigate the other, then place another gate to move to the previously gated location, saving 2-3 actions in the process. He might also put a gate at a friends's spot, move a few locations, then gate somewhere around his new spot, allowing the buddy to move 3-4 locations in one action. For Luke Open Gate is a much more reliable staple than for other folks.
• Norman Withers doesn't have as much flexibility, but he tends to dig DEEP into his deck every map, when he does find Open Gate he can often play it for free, which is great incentive to just drop it in order to save himself or his friends just the one action or so (while also digging even deeper in the deck!).
• Daisy Walker can run very fast, and she can get the pieces quickly with her Old Book of Lore engine, efficiency wise they are a bit worse for her than Luke and Norman but as for deckbuilding and finding the bits it's smooth sailing for her.

I frankly wouldn't even try Open Gate for other characters than the above, Akachi Onyele and Agnes Baker aren't fast enough and it would wreak havoc on their tight decks and cost curves. Jim Culver doesn't have the deck-space and there's no synergy, he doesn't struggle so much for actions as for consistency, same with Father Mateo. Sefina Rousseau likes to mess with her events and there's already a thousand good options. Diana Stanley has other stuff to do with her time, movement support is something that should be directed AT her, not From her. Patrice Hathaway can certainly find them fast, but they'll drip from her fingers long before you can put them in the right place and actually set up a good network.

In a 4-player Standard campaign, I always start my deck with 3 of these, and remove them somewhere before the halfway point of the campaign, and it works out well for me each time.

To start with the upside, if I draw 2 Open Gates, it routinely saves the group 3 actions a game, sometimes less, frequently more. In most campaigns' early missions, you're in the "explore" phase of the mystery, where you are wandering around town/campus/jungle flipping locations and collecting clues. Since you're low-xp characters, you don't have much of your jank, but the game accommodates you with easier shrouds and monsters, many of which are beatable with just base stats. It's usually effective for your group to split up, but there's always that Act that says "investigators at <Location X> spend clues as a group to advance/resign", where the party has to get to a specific spot. Open Gate lets at least one teammate teleport there, which may even let you advance the Act a whole turn sooner than you could have otherwise.

As for the fail cases, If I draw 1 Open Gate early but never get its partner, then I'm out a card and resource, which is a fair price for a failed gamble in this game. If I draw it late, I can pitch it to a treachery. It may be suboptimal, but it's never dead.

The card definitely gets worse as the campaign goes on, both because missions start to become "charge forward to your inevitable doom" with no backtracking, and also because your bottleneck changes from movement action economy to succeeding repeatedly at difficult tests, and Open Gate doesn't help with that.

Like Flashlight, I think this is an excellent level 0 card for your starting deck that you swap out later as they become obsolete.

As the other reviewer said this card is printed for Luke and only him. His ability to play an event in a connected location is just so versatile. I've recently finished the Return to Night of the Zealot campaign on Expert with Luke and Zoe and Luke was definitely a lifesaver! Especially, in the last scenario he was able to set up a link between a ritual sight and another location in the woods to help Zoe skip the cultists! And he himself Shortcuted through the enemy. The deck I used arkhamdb.com

Inference: I wouldn't use the gates outside that mystic.

Moreover, I feel like Open Gate has such a synergy with Arcane Initiate.

And... A question: If an investigator with an enemy moves through a gate, will the enemy follow him to that location?