Quite good, though maybe not exactly essential
This DLC adds a bunch of fairly useful abilities to the game, like the "great power" system (if you're planning to play as one of the bigger nations). There's another DLC out there giving you the ability to "threaten war" to slowly annex provinces, and I've come to use it almost constantly. I imagine threatening over breaking alliances will be just as useful.
Similarly, personality traits add a bit of extra spice to gameplay, and having queen regents seems pretty darn useful to sidestep painful regency periods.
One of the first DLCs I'd recommend getting, provided you already have the essential "Common Sense" and "Art of War" (otherwise go for those first).







