I've been playing Killzone 3 for 2 weeks now and here are my impressions/review of the game.
As a huge Killzone 2 fan, I am happy with GG that they added the Coop single player mode. Nothing is more fun than playing Killzone 3 with a buddy. However, after beating the SP in 6 hours on HARD mode, I can safetly say I will not come back to it again, since it is a very forgettable experience. When compared to Killzone 2, Killzone 3 SP misses the mark. Killzone 2 wowed gamers with crazy graphics and a gritty campaign with a memorable villain (Visari). However, while KZ3 has more varied (and beautiful) environments, the plot itself has alot of potential, but is handled poorly by sub-par voice acting, and 2D characters. I still have no reason to feel emotional connection with the ISA or Helghast, since their characters do not develop past the "pissed off" and "sterotypically heroic" behaviours. However, I can say that the campaign does provide a fun one time experience.
Oh and I forgot to add: the sound in the Single player is terrible. The music plays way too loud over the voices, and at times (especially in dramatic moments) its plays too low. Also lip synching can be off.
Now to the Multiplayer, KZ3's biggest strength. First I will start off with the positive aspects. The framerate and stability is much improved since launch due to GG patching the game. Moreover, there are now 3 modes as opposed to 2, with the new one being Operations. Operations makes you work with other people to take down Enemy AI in a variety of objectives similar to the Warzone MP mode. Warzone remains the same, and weapons as well as classes seem more balanced than KZ2. New additions to MP are jetpacks and mechs which are always welcome!
Now to the negative aspects: Controls are more streamlined. What do I mean by that? They have a less weighty feel to them than KZ2, which was what made Kz2 so different than other 'twitch' shooters like COD. In addition, the multiplayer has very few new additions in comparison to KZ2, which makes it extremely similar. Now that may not be a bad thing, but as a person who played Kz2 MP to death, I can safetly say that I got bored of KZ3 MP really quickly. But that is just me, opinions on this may vary. Lastly, the maps. There are only 7 maps that come on the disc, and 3 operations maps. That is a very low number, and unless you buy the DLC, you will get bored fast.
To sum up, Kz3 is a really fun game and pretty to look at game, and should definitely be purchased by newcomers to the franchise mainly due to the Multiplayer. However, Kz2 veterans may wish to save their money due to the lower quality campaign and very similar MP.
Suggestion: Buy for newcomers to KZ franchise
Rent for veterans of KZ2