I bought this as well based upon this post. Good game, yes frustrating at times because of the constant attacks. I've managed to establish some good defensive points that the enemy just pretty much falls upon and dies, and if things get critical I've got the Companion Cavalry as a mobile force.
Those Athens raids can be stopped if you take their nearest town, and I would also recommend that once your interior is safe, or close to safe, start tearing down walls so you can create additional troops for attacking.
One thing I would like to see for this game is sandbox mode vs. a story driven campaign. I'd like to for the AI to be attacking each other as well. As far as I can tell, its Philip against the word.
But good game, fairly addictive, and lots of potential.