This is a stellar game. It's great to play and a huge breathe of fresh air as far as "co-op" game-play goes. I hope more games adopt the format of "fun to play solo, great with friends."

Arrowhead, Thanks for some of the most fun I've had playing games since I was a kid.

The rest of this review is deprecated as Sony has packpedelled in the time since I originally wrote this review. I've left it here for historical purposes.

However...
Sony is attempting to leverage the HD2 player-base to boost their overall PSN user-base by mandating users associate their HD2/steam accounts with a PSN account. There are many reasons that this is bad business practice, erring on the side of unethical. I'll list a few here.
1. This 'mandate' was not made known upon game launch, and instead was adding after the fact.
2. The user-base that the game was made available to purchase was worldwide. Sony has very liberal geo-restrictions (many countries are blocked) on where people can sign up for/utilise PSN accounts. This mandate in function 'removes access' to software that people have purchased, for an arbitrary business decision that was made after the game was seen as a success.
3. There are no realised 'user benefits' to this association of accounts. there are no in-game perks announced, or any cross-play associations. There is no 'account progress' summarising happening for those that have purchased the game in both places, and there are no "benefits to the gamer" that will be seen as a result of this change. Sony claims it is for "Security Reasons", but Sony has a very poor track record regarding their cyber security, as their track record would show they are likely to be breached every 3-5 years.
4. Finally, it would appear that Sony, as the publisher of this game, has gone out of their way to be deceptive regarding communications of how 'mandatory' this association would be. It did not appear to be mandatory at time of purchase, and the communication now seems to have been changed retroactively to suit their corporate agenda.

Sony is attempting to grow the PSN userbase by capitalising on the significant and dedicated PC Gamer user-base of HD2.
Sony is attempting to leverage Arrowhead studio's developers love and passion for their craft, and this fun, endearing, goofy, and intensely stressful (On level 9) game to boost their long-term sales by driving membership growth of their PSN service in hopes we just 'end up buying stuff from them', rather than growing their service organically by providing useful features to us, their members.

Arrowhead Studios, I hope I am able to change this rating to Positive in the near future. Thanks for some of the most fun I've had playing games since I was a kid.

Disgraceful Conduct, Sony. Please report to your nearest Democracy Officer.