I've been theory crafting a Crossbow Sniper Gunslinger and I keep going back and forth on this feat.
You do a worse Leap and a "Nimble Doge" in one reaction, but then you have to spend an action to get back up, which sets you back to a minor net loss in terms of action economy. You can mitigate this at level 7 if you get "Kip Up", or 15 if you delay your Legendary in Stealth for a Legendary in Acrobatics and "Nimble Crawl", neither of which are ideal.
This is without taking into account that it triggers half as often as "Nimble Dodge" since it has to be a ranged attack, and the fact that I have to be mindful of any other creature that may act before me, because I'm not just going to give them a free flatfooted. In practice I'll be using this reaction about a quarter of the time as Nimble Dodge even when i can leap behind total cover.
There is also the elephant in the room of shooting while prone. I'm willing to admit I may be blind here, but I don't think they brought back the rule that let's Crossbows/Guns shoot while prone without the -2 penalty. So even if you start the turn prone with an unloaded weapon, reload+take cover is useless since you have stand up to fire.
None of the stabilizers seem to negate that penalty either. The Shielded Tripod let's you take cover in that square, something you could already do while prone. If I'm reading this right, that means all existing stabilizers are designed to be used while standing up.
Even without the prone shooting issue, since I play at tables that frequently homebrew that exception in without me even having to prompt them, it just feels to me like this feat isn't good even on the subclass that seems like it would get the most use out of it.
If you frequently encounter ranged attackers, then it isn't a terrible choice.
As a Sniper, you want to be near cover anyway, so this often allows you to fully negate an attack by just jumping into full cover. This comes at the cost of messing up your entire routine, though, as you pointed out. But if that ranged attack is something really nasty, this makes for a solid panic button. Soak a couple of hits to help out your frontline, then jump into cover. After all, a dead gunslinger deals no damage.
It's not something I would use terribly often, but it is certainly nice to have.