Judging from the demo it would be a fun 5 hours. Very satisfying game to play.The sword mechanism works so well. Between it and Dynasty Empires I'll probably go with Empires because of longevity and pick this one up later.
Here is a review that doubles the 5 hour estimate.
Yes, JokerJawz, Journey is an amazing game but if you walked in a straight line and through the obsticles, without going off course and looking for all the bits and pieces it would be 2 hours at the most.
Like many have said, while £40 may be steep for a game which has 6 hours of gameplay, they don't mean collecting anything by doing one runthrough without dying and skipping cutscenes. Even if you skip the cutscenes, but want all the trophies, it'll take you around 40 hours at best.
Some of the trophies are nuts, such as there's a Gold trophy which expects you to S rank everything...