Theres plenty of material out there of Shadow of Mordor for everyone to make their own minds if the game is something they would like to buy imo.
The latest trailer was filled with E3 game of the show shit, if that rocks your boat. The general word fromthe journalist of the biznes seem pretty damn positive.
I have faith in Monolith in recards of the port also, so with that price its a kind of a no brainer for me atleast.
That being said, pre-ordering is always a risky move and especially with GMG and their super aggressive pricing on titles i do see why it would seem like a too good of a deal to pre-order with such deep discounts...i dont believe Shadow of Mordor will be anything like Colonial Marines though.
How Gearbox handled Colonial Marines is luckily a rare thing.