I really liked the undead/pirate theme since all the way back during the first edition Prime. The only problem was Skarre was really ugly, but fortunately this was remedied with a resculpt.
Speaking of resculpts, I prefer the original Satyxis Raiders, despite being a bit more fragile. I wish this unit had seen plastic, since the material would have made those spindly bits way less scary. Still, I like them, and gave them new horns that were a bit more durable.
Keeping the older Satyxis had the added benefit of the Captain's look being a lot more proportionally heavy.
The Leviathan is just a really fun model- I really liked the irregular, actually steampunk look to the first few books of Warmachine, and while standardized chassis designs make sense as an army, I preferred the unusual designs as opposed to one more robot with a new set of weapons.