General
 
    General user interface improvements.
    Various performance improvements.
    Fixed issue where a door may not function properly if a Xeno was killed while opening it.
    Addressed issue where players could become stuck in a close encounter after killing a Lurker that had pounced them.
    Fixed collision issue where bullets would not pass through certain open doorways.
    Fixed an issue related to clients incorrectly interrupting Xeno melee encounters.
    Addressed an issue where doors would sometimes not open properly.
    Addressed an exploit where players could melee while throwing a grenade or placing a claymore.
    Fixed some collision detection issues that could result from a close encounter.
    Prevented campaign pop-ups from appearing outside of campaign.
 
Campaign
 
    Fixed an issue that could prevent NPCs from getting on the elevator in the Sulaco.
    NPCs no longer attempt to open doors while being welded.
    Fixed issue where Raven could sometimes pass through welded door.
    Implementing a message to warn players that campaign progress will be overwritten if they try to start an offline campaign game from within the co-op campaign UI.
    Adjusted the distance between players before they're warped to the location of furthest player in co-op.
    Fixed issue where torch would sometimes appear incorrectly to co-op clients.
    Fixed issue where difficulty could sometimes become stuck incorrectly after switching modes.
    Fixed issue where co-op player would not recover properly after being saved from a close encounter.
    Fixed issue where Russian players could not drop into a co-op match in some missions.
    Updated late-game close encounter moment to disable player input, which could cause them to become stuck.
    Splitscreen: Weapon Radial menu no longer appears for other players when the pause menu is opened.
    Splitscreen: Fixed issue where if the Game Menu is opened while accessing the Weapon Radial, it stays up on does not function properly.
 
Multiplayer
 
    Resolved issue where campaign Motion Tracker could incorrectly in multiplayer loadouts.
    Fixed issue where clients would sometimes be invisible after spawning in No Hope in Hadleys.
    Multiplayer teams are now randomized (parties excluded) if percentage difference in scores is greater than 15%
    'Switch Teams' option removed from the Pause menu.
    Corrected issue where server and client could get out-of-sync when switching out of a power-up while firing.
    Fixed issue where controller would vibrate during the scores screen if Rage ability was active upon match end.
    Fixed issue where Cloak ability would not conceal the Lurker when walking or jogging.
    Corrected bug where clients appeared to spawn outside of world before match start.
    Removed placeholder text from appearing on scoreboard in certain situations.
    Improved camera transition when Xeno enters a vent.
    Fixed issue where Xenomorph HUD could sometimes appear in the wrong color.
    Fixed issue with Spitter acid sometimes preventing players from deploying a Sentry Turret for a short while.
    Spitter's "Acid Spray" now originates from the mouth.
    Escape: Fixed issue where Xenos could spawn in unplayable space.
    Escape: Fixed issue where Xeno players could lose functionality if warped to next area while in a vent.
    Escape: Addressed issues where players would spawn with no weapon if they were the last Marine to die in Escape.
    Escape: Fixed issue where Cat-Like Reflexes ability would not properly complete in an Escape match.
    Escape: Improved timing and placement of warp locations in Emergency Evac map.
 

 
First off, due to me breaking NDA, I can't provide any proof that I'm not just talking out of my ass. But I figure you'd be interested in hearing what I have to say regardless. I've been on the project for around a year and a half, so some of the following are things I've heard from more senior guys.
 
Pecan (the internal codename for ACM) has a pretty long history. SEGA, GBX and 20th Century FOX came to an agreement to produce an Aliens game around 6 years ago, after which SEGA almost immediately announced it, long before Pecan had even started production. The game has been in active development in the past, only to be shelved in favor of another project (Borderlands, Duke, etc), and each time it was resumed it would undergo a major content overhaul.
 
SEGA, naturally, wasn't super pleased about the delays, but GBX got away with it for a long time and the contract between SEGA and GBX kept getting augmented to push the projected release further and further back. The last time it was resumed, GBX outsourced a good portion of the game to outside companies. Initially, the plan was for TimeGate to take the majority of campaign, GBX would take MP, Demiurge and Nerve would handle DLC and various other focused tasks. This decision was made mostly so that most of the developers at GBX could continue working on Borderlands 2, while a small group of LDs, coders and designers dealt with Pecan.
 
Somehow the schedules for Pecan and Borderlands 2 managed to line up and GBX realized that there was no ******* way they could cert and ship two titles at the same time. Additionally, campaign (which was being developed by TimeGate) was extremely far behind, even as Pecan's Beta deadline got closer and closer. In April or May (can't remember which), Pecan was supposed to hit beta, but GBX instead came to an agreement with SEGA that they would push the release date back one more time, buying GBX around 9 mos extension.
 
About 5 of those 9 months went to shipping BL2. In that time, TimeGate managed to scrap together 85% of the campaign, but once Borderlands 2 shipped and GBX turned its attention to Pecan, it became pretty apparent that what had been made was in a pretty horrid state. Campaign didn't make much sense, the boss fights weren't implemented, PS3 was way over memory, etcetcetc. GBX was pretty unhappy with TG's work, and some of Campaign maps were just completely redesigned from scratch. There were some last minute feature requests, most notably female marines, and the general consensus among GBX devs was that there was no way this game was going to be good by ship. There just wasn't enough time.
 
Considering that SEGA was pretty close to taking legal action against GBX, asking for an extension wasn't an option, and so Pecan crash-landed through certification and shipping. Features that were planned were oversimplified, or shoved in (a good example of this are challenges, which are in an incredibly illogical order). Issues that didn't cause 100% blockers were generally ignored, with the exception of absolutely horrible problems. This isn't because GBX didn't care, mind you. At a certain point, they couldn't risk changing ANYTHING that might cause them to fail certification or break some other system. And so, the product you see is what you get.
 
Beyond gameplay, the story has been raised as an issue several times. I can't really comment without feeling bad beyond saying that the script was approved by 20th Century FOX, and that the rush to throw a playable product together came at the cost of the story. Campaign does a pretty bad job of explaining a lot of the questions raised at the start of the game, and so hopefully there will be DLC to flesh that out a bit better.