Okay so I just finished my first grand campaign (long one) as Marathas, normal/normal difficulty (it was my first Total War game really).
Mixed bag as of now... I want to like it, I love the battles, but the campaign itself was dead.. dead... dead.
The AIs sat around doing nothing much for most of the game. Wars were declared in the first quarter of the game (before 1725), no peace was ever made after that but no progress seemed to be made either by anyone. Sometimes a region would shift momentarily between France and England (in north america) or France capturing Alsace-Loraine for 2 turns then losing it... The Spanish had a few strange holdings... The most exciting thing was Ingrian rebels holding St. Petersburg for most of the game (although I didn't see a flag and I don't think they're an emergent nation or anything.. booh).
But yeah, the AIs sat there doing nothing exciting and not interacting with me at all except to ask me again and again for the same regions in exchange for some random colony I didn't want.
None of them changed government type at all. That was disappointing one of my biggest disappointment for some reason. No faction emerged at all either.
Does it become more involving if I play on hard/hard? I don't think I want to play Very Hard (mostly mathematical advantages for the AI, especially in battles, probably on campaign map too).
At the end, I was rolling in cash. I had finished my objectives by the late 1740s, so I basically roleplayed a bit, trying to help my allies in Europe by sending assassins to kill our enemies' generals and scholars... Helping my ally France who had lost Montreal to the Iroquois... But I was so rich. At the end I had 6,000,000 ducats and was making 100,000 per turn at the lowest tax rates.
I just didn't want to get into a slugfest with the Ottomans (my friends too) or more likely the Russians (indifferent) because I didn't see the point. I decided to sit back instead and see what would happen with the AIs. Do they do anything if I'm not involved too much? That was my question, and the answer was pretty disappointing.
Also, I have a really good computer, still, towards the end, the AIs took quite a while to do their turnset. Turns without battles are quite short when you've already upgraded everything to the maximum... And I reckon years 1775-1799 were spent mostly waiting for the AIs to take their turn (yes, show enemy movement was turned off).
I just need more interaction, more surprises. I guess I'll try hard/hard and see...