A friend of mine is running the Emerald Spire, and I'm a swashbuckler. The class has some . . . kludgy design? Like, I can use their Dex for melee attacks (sorta like Weapon Finesse), but only with light- or one-handed piercing weapons. So that means a swashbuckler can wield a morningstar (and actually needs to if he ever wants to fight skeletons), but can't use a cutlass like a proper pirate. Heck, I can 'swashbuckle' with a pick. I don't know why they didn't just make it Weapon Finesse like normal. I guess they wanted to avoid spike chain swashbucklers? *shrug*
That said, the class works well when I can take off my Game Designer hat.
Another PC had the . . . whatever the barbarian/bard is called. He grants rage to his allies, instead of a flat bonus. Which was mostly useless to me, the swashbuckler, since increasing my Strength is fairly pointless. And was mostly useless to the party's wizard. The cleric kinda benefited, but I don't see how it was better than a normal inspire courage.
As a Pathfinder book, I suppose it's fine. I've just never been a big fan of mechanical fiddliness, and this book seems to have a lot of it.