[Taqwus]

The differences are fairly substantial -- eras instead of themes, rebalancing of costs (fortress cost and incomes increased, troop and commander costs less changed ergo cheaper), more differences between national access to magic paths (much more restricted randoms, so it's harder to diversify), more spells being nation-specific, and so forth. AI behavior is similar to before, but it will actually build fortresses now and makes heavier use of national troops. Micromanagement's also improved, with automatic adjustment of taxation (overrideable) based on unrest, and the ability to set mages to monthly-cast site-searching spells and let them be...

There's a point of contention with some arguing that the power of high blesses reduces the number of competitive strategies under certain conditions (notably, cramped maps where blitzing with powerful sacred units are difficult to counter if, say, you've instead piled points onto scales). If it's agreed to be a problem, to a certain degree this can be ameliorated via mods (increasing the effects of scales, for instance, to make it harder to pay for those ultra-blesses).