The main issue I had was that the Arabs are technologically ahead of me and even my levied swordsmen don't match up well against Mamluks - which were also fast enough through hills to catch units I thought were safe. The AI did make my life easier with some pretty terrible play - it was good at sniping units, but avoided firing at my cities with crossbowmen and just sent Mamluks around pillaging trade or beating up levied swordsmen instead of attacking, while a Great General sat miles from any units doing not much. For some reason it did however suicide a spearman against fully-healthy, walled, garrisoned Tikal.
Also, they've finally fixed Repair Outer Defences so that it doesn't randomly vanish as an option.