I have! I'm not actually much of a fan of it, myself. At least not in the most recent iteration it's had.
(Mercer has repeatedly updated it, even after the campaign's end)
It's kind of a weaker Battle Master with a focus on ranged/firearms, with the damage bonuses of Superiority dice frontloaded into the weapon overall (because Exandria, like many TTRPGs, makes Guns do way more damage than other weapons and then makes other mistakes to compensate).
Beyond that they get initiative bonuses, rapid reloading, and the ability to quickly "Fix" their weapons which rely on a misfire mechanic to make using guns as annoying as possible (Because the archetype exists only in relation to the weapons that define it, of course).
Misfire, in particular, is so incredibly bad as a design for a character that's supposed to make 4 attacks per round. Why? You critfail 5% of the time. So your chances of rolling at least one natural 1 in a round are about 18%. Increasing the misfire rate to 1s and 2s makes it about a 34% chance.
By Misfire 3 you've got a 47.8% chance of misfiring if you make 4 attacks.
Like... you have about a 37% chance with most firearms of jamming EVERY ROUND that you make 4 attacks. God forbid you should Action Surge!
There's not a lot of "Gunslinger" to it. You have a fighter with a gun and some maneuvers and... that's it. You could make a more mechanically effective Gunslinger in Exandria by just -using- a Battle Master Fighter and carrying several guns so you can swap firearms when they inevitably jam. (Grappling Attack, Lunging Attack, Riposte, and Sweeping Attack require melee, none of the rest do)
Though in large part that has to do with 5e's granting of archetype features spread out thin over the fighter class. You don't have a lot of room to actually -explore- something as previously expanded on as a full character class. You can -touch- on ideas, and create some general themes...
But then the need to negate the major penalties Mercer created for firearms in exchange for big damage just really ate up a bunch of slots, y'know?
It's why I've got my own Gunslinger -class- for Martial Artistry.
View attachment 384607
There's a lot more room in a full class for the tropes and identity of a gunslinging character. Not just Quickdraw, but things like hitting the deck when someone's firing at you. Making better use of cover than most characters 'cause gunfighters diving behind tables or hiding behind pillars in firefights is an important visual concept.
There's even Hognose Flop in there for feigning death after taking a hit, then they roll you over and you shoot them point blank.
And because the class has that much flavor of it's own, it can support subclasses of different kinds of gunslingers (Bushwhacker, Desperado, Maverick, Pistolero) so you get more character variety.
Anyway... yeah. It's a whooole thing.
But before anyone thinks I wanna yuck their yum: It's a different style and a different goal in the end.
The Gunslinger Archetype was made for Percival de Rolo. It was meant to facilitate that campaign's specific storytelling methods and concepts and there's nothing wrong with people liking or using it.
I just feel there's more that can be done in that design space. And find WotC's devotion to trying to just have the 13 base classes with an ever-expanding list of subclasses is not the right direction to go for getting deeper into character design. Shallow and wide isn't the worst thing... but it's not the best, either.
