I love Warmachine, but I had a very hard time deciding on a Hordes army until I started seeing models like Lord Carver or the Blackhide Wrastler. Pigs 'n' Gators! I picked up the book this weekend, and ... well... it's pretty cool. I don't play Mercenary armies in Warmachine, so maybe this experience is shared, but I was a bit disappointed by the division in the book. It's Pigs OR Gators, for the most part. That's fine, I can understand that, and I would assume that Rhulic Mercenaries and Magnus would not play nice together necessarily.
What kind of made me sad were the units that I absolutely cannot take as a particular mercenary force. Playing pigs? Sorry, no Feralgeist. Playing gators? Sorry, no Gudrun the Wanderer. Playing anybody? Sorry, no Lanyssa Ryssyl or Dahlia Hallyr and Skarath. That last one just breaks my heart. I tend to pick armies based on the models and not the rules, so to find out that my favorite models in the "faction" can't work together makes me sad. It pretty much dooms me to have to start two Minion armies, plus another Hordes army if I am going to get some of the other cool Minions units/solos.
Then again.... I paint more than I play. I should just buy the models, paint them, and stop whining. After all, not playing Legion, Cryx or Cygnar didn't stop me from getting Vayle, Skarre or a journeyman warcaster.
In terms of the book, I was very entertained by the background stories. Much like the other PP "Forces of" books, the art is big and bold, and the rules plainly presented. It seems a little light compared to, say, the Protectorate or Khador books but it's a new faction so that's to be expected. I really would have preferred to see more painting and hobby content, including maybe some close ups of the models to show details that aren't really visible on the web. That would certainly give the book more value to me. Pages-wise, it's about 2/3 the size of Codex: Space Marines but with much more color at exactly the same price point.