I am not seeing some of the complaints from the above posts. As for the hard difficulty diplomacy I am in love with it. In Rome 1 I would play on the hardest difficulty and of course it was pointless to even try anything besides spam trade treaties. In this game I can actually, and generally do, make alliances or even client states. I am able to do this with people early and late game. In the first game. Rome 1, I was never able to make one. As for the generals being "arrow immune" I BEG TO DIFFER. There have already been a couple times, actually the first few hours after launch, where my general is safe behind my lines but the enemy range will shoot at my general while our lines are fighting (Edit: Haha the first time actually my general was in a hoplite group in hoplite formation which should of all things be awesome against arrows!). Each time the first few casualties end up being my general which is incredibly frustrating but fun (or !!fun!!).
Some interesting things I see with the AI are civilizations content to sit at their one town for the first fifty or more turns and then suddenly go on a rampage taking five of their neighbors on before settling down to nothing again. Your allies actually do what you ask and are always trying to help with armies (again playing on hard) which is amazing coming from Rome 1. Of course having anyone within a certain radius, as opposed to requiring people be literally standing next to you, be drawn into the fight is awesome. Many times I have gotten help by initiating fights somewhat near passing friends.
My complaint, or learning curve, having come from Medieval 2 and Rome 1 is the building system and the province nonsense which was mentioned earlier. I guess it will take getting used to.