Let me preface this by saying, I was pretty excited for the co-op in Lost Planet 2.  The girlfriend generally loves playing co-op games, so we decided to split-screen through the campaign together.  The next few hours were pretty disappointing to say the least.  
 
First, the interface of the split-screen is pretty dumb.  The screen is separated as if it were a 4 player split screen game.  However, the 2nd and 3rd player screens are all black with a minimap in them.  Even on a 50 inch HDTV we could hardly see what was happening.  Also, the game always shows a big red X on the closest enemy in your field of vision on your HUD, which would be helpful if your crosshair wasn't also a big X.  Second, the slow animations were really making it tough to do what we wanted to.  The second and a half animation on the grenade throw is especially annoying (intended design choice, monster hunter, eastern game design, etc...). Third, and most importantly, you can't use AI partners in split-screen, or if you can we haven't found a variation of the options that allows it.  This is a huge pain in the ass because the game doesn't scale down the number of enemies if there are less than 4 people playing.
 
Basically, girlfriend and I easily make it to the mine at the end of 1-1, get rocked during the "keep all these nodes activated for 90 seconds while infinite enemies respawn and a few VSs come in to help destroy you" part of the chapter.  The timer gets down to 27 seconds, a VS drops in, annihilates us repeatedly.  Game Over.  Now we have to play through the 25 minutes of the game that we already beat again.  and again.  and again. and again. After the 4th try of this nonsense, we stop playing.  Girlfriend thinks it is the most poorly made game she's ever played.  I can't say I blame her for thinking that having just been through the most frustrating two and a half hours of gaming I've had to endure in a looooooooong time.
 
Honestly, all the technical griping could be set aside if the game were actually able to be beaten in local multiplayer and/or if we could actually play the game together the way it was meant to be played, with 4 players (human or otherwise) running around killing giant bugs.  Also, if there's some variation of the options that allows us to play split screen and have AI helpers, please let me know (Can't get online at her place, the one with the giant TV, because her ISP is shit and requires her to pay an extra $20 a month for an extra IP).