In the last three days me and my girlfriend went throught the whole Haradrim cycle with our four mono-sphere decks (that have right now succesfully dealt with little changes with almost all the existing quests, we are tyring to beat them all). I think it might be the best cycle I ever played, even better than Wilds of Rhovanion and the Ered Mithrin cycle, both as narration and as quest mechanics. The Mumakil was the easiest quest for us and the most challenging (albeit still in a good and interesting way, not frustrating) was The Crossing of Poros. The Black Serpent was not nearly as difficult as I thought it would be by reading around.
In any case great fun, this game keeps just giving.