Link to the full review: http://www.gamespot.com/reviews/galactic-civilizations-iii-mercenaries-review/1900-6416389/
Essentially their reviewer condemns the expansion for breaking the core premise of GalCiv -- they skip the normal means of acquiring a ship (developing the tech you need, designing and building it) by providing a must-have nuclear option for getting ships that overpower non-merc ships and have powerful bonuses to boot, making researching techs and designing ships all but useless.