Well, I was surprised at the size of the Mongol horde when it arrived. Surprised and somewhat terrified - my fledgling eastern empire which was won by crusading is in severe danger of being trampled under the hooves of many many Mongol ponies!

The horde moved up and down the coast of Jerusalem for a few turns, laying siege and then moving off - I was initially a bit concerned, but eventually they did decide on a target, and I lost Antioch to 4 stacks (I was kind of hoping the siege AI would be as ineffective as it was in BI with the Huns, but I'm pleased to say they trounced me), and now my fortress to the north of Antioch (who's name escapes me at the moment) has just survived an attack, but will surely fall at the next.

I did discover a bit of a cheesy/gamey tactic with English longbowmen when defending sieges - sometimes when you deploy them, their 'plant stakes' icon becomes active - you can put them behind the gate and deploy their stakes = instant Mongol cavalry shish-kebab. However, this seems to be a bit random, as in a previous siege the longbowmen only had the fire arrow ability available during deployment - this could be seen as a bug rather than an exploit, but it does give the English a huge edge when defending against cavalry heavy siege armies.