The A.I. is great for learning the game.
Since learning the game takes a long, long time time...well...i'd say the A.I. is fit for its purpose.
Particularly the concept that everyone is bound to declare war on you sooner rather than later, and all together.
One thing that I don't understand though - why do A.I. nations far away from you declare war on you, do a few distance spells (funny how they seem to know exactly where to launch those spells to target your armies even though they're not supposed to know where they are), and then nothing?
The only thing I really dislike is when they cast that unnatural aging global enchantment really early, and you see all your nice expensive leaders, prophets etc get afflictions and die

If only leaders could be immune to global enchantments...