I have just completed a few games playing Scotland on m/m, h/h, h/vh and vh/vh.

A few observations:

It is a great game and the developers should be well pleased with themselves. I am sure I will spend hundreds of hours absorbed.

The difference between levels of difficulty is not so apparent as it was in RTW. The difference was readily apparent in Rome because the AI factions seemed to mass produce units at higher difficulty levels and this doesn't happen in M2. I am glad it doesn't. I have hated this type of "advanced AI" since battling the Hojo hordes playing Shogun.

In my games I perceived the AI factions had a lower threshold for declaring war on me on harder settings.

I was excommunicated quickly, inquisitioned and promptly had unrest in my cities several times on vh/vh for not following instructions from the Pope. The follow up for not behaving well on m/m didn't seem so aggressive - anyone notice this?

There is a general problem with the AI on all difficulty levels. It seems whole AI stack armies will sit back and let you seige and sack cities when they have a decent shot at beating my invading forces or certainly seriously weakening them. I wish the AI would attack me when I invade and threaten cities.

I would write more but I'm too busy campaigning!