Finally beat this one yesterday. The game seemed incomplete. A lot of new ideas and scenarios but it seems as if they weren't tested enough by the time of its rushed release. Lots and lots of questionable design choices that make it cheap rather than genuinely challenging.
problems like random, unfair AI enemy spawning, unclear objectives, awkward level design, faulty AI bot control, and more problems that shouldn't happen in current Gen gaming. Killzone 2 and 3's campaigns are superior in nearly every aspect other than graphics.
the multiplayer is awesome and the campaign overall is devisive but not absolutely horrible. Shooting mechanics are solid though, and it looks great, despite being framey. Good buy for $32 to tide you over until infamous.