I've got to say I caved in and bought it, mainly because I have no games to play at the moment for my PS4, and my rig is dead (RIP).
First impressions are positive, I played the first couple of missions solo and it was a solid game. Then I partied up with a couple of other guys and have been playing through the story missions and it has made the game so much better.
I'm currently 3 hours in and level 8 out of a maximum of 20 so leveling goes pretty quick, it seems like the story missions are just a tutorial and the game is trying to get players quickly to 'end game content'. This isn't to say that the story missions are easy, it does start to get pretty challenging and boss fights require teamwork to get through.
I think this game will live or die based on its end game, so it will be interesting to see how that goes when I get there. If the end game content is shit and the leveling is as fun as it has been, I will still have gotten my money's worth from the game.