While all of the patches thus far have been pretty substantial, patch 5 has brought a free new playable faction and Steam Workshop support with it.
The full patch notes are here, but the summary post on the forum states:
This patch contains a large number of improvements across pretty much every part of the game. Among these are a number of optimisations to Campaign Map performance, which improve framerates with the fog-of-war and when there are many armies, navies and agents on-screen. We’ve also sped up end-turn times in situations where the player has multiple allies.
There have been further improvements to diplomacy as well. The campaign AI now encourages factions to form allegiances based on personality, perceived threat and the existing balance of relationships the faction holds. Players can also see relationship information by hovering the cursor over factions on the map in the diplomacy screen.
We’ve also reduced the chance of AI armies standing close to the player in Forced March mode – thereby reducing their chances of being ambushed – and any garrison of armed citizenry will now reinforce friendly armies in battle outside their settlement.
Finally, we’ve added tooltips to Agent Actions, which reveal their normal and critical success and failure chances. This gives you a much clearer picture of the potential outcomes.
All of this is very welcome, especially giving us the Seleucid faction to play for free, but Creative Assembly have stated that they’re going to continue with the rapid patching, both with changes and fixes to gameplay features and continued work on stability and performance.