While this isn't the first update the brilliant yet technically "eccentric" game has received, it's certainly the biggest (with "over 70 bug fixes") and most wide-ranging.
A number of crash glitches have been "solved", along with audio, save game and assassination fixes. The AI has been improved in naval combat, and, best of all, the AI can now attempt naval invasions of your territory. Apparently Creative Assembly are finding this very hard to balance, so they won't do it often, but they'll do it occasionally, which is better than never doing it at all.
God willing, this update will be out in the "early part of next week". Shame it doesn't address the game's two biggest problems - hanging on ports and an overall slowdown in the later decades of a grand campaign - but hopefully they'll be addressed next time.