Get this installed before you play the original game because it adds so much and its helpful
First off the additions such as the caravan and spells are great however the spells are annoying to those who completed the game orginally. Because the spells require relics and charms which you find randomnly throughout the game. However this is not helpful for those who went through the game and thought of the relics as either a quick source of cash or a cheap upgrade to items, so those who played the original before getting the expansion will find they lack most of the relics and charms required and will either have to go back and search through the massive areas which takes hrs! or they can give up on getting spells. -which is hard because once you begin to play the expansion campaign you'll find that most the weapons and armour are fairly crap! so you need those magical extras otherwise you face a hard fight!
The world of Hades is a dark one which is cool and the monsters are not only a lot stronger but also more scary in a way - as you'd expect for the Underworld. I enjoyed the new area especially once you reace the field of Elysiem (sp?) which to those who have played will know its where dead heroes go, its so fun because fighting hordes of monsters is A LOT more fun when fighting alongside allies. My favourite bit is the frontlines of the demon territory where they have like a dark aura surrounding them and you fight through a military encampment with towers and connecting bridge things. Although i couldn't help thing the combat could have been improved by being on consoles allowing for more strategic depth than 'click to kill' basics.