Well, a patch was just released.
List of new things/fixes that have been found so far as followed.
*Powershooting (This was a glitch which let you fire off an entire clip from the assault rifle/Uzi at once.)
*Going back to regenerate boomer bile with a respawn. (This is similar to how they fixed being able to refill your health if you respawned.)
*Ghost scratching/clawing (This is the act of going far enough from the survivors to respawn and hitting the left trigger button, followed by immediately hitting X to respawn. You stay in ghost mode while hitting the survivors.)
*Infected hud is different. You can also now see how close someone is to be using their special attack again IE. Boomer bile.
*Everything has a higher chance of spawning/appearing. Mollies, pipebombs, common infected, health kits, propane tanks, ect. Everything EXCEPT... Tanks and witches. Apparently that was just from the servers themselves, and not the patch.
*Less damage from common infected (Unconfirmed.)
*A lot of the respawn rooms in campaign (At least the ones in No Mercy.) Can't be opened/broke down. You CAN spawn in them as infected, but can't get out. (Unconfirmed on other maps.)
*Spawn times seem to be changes a bit, more likely to get a 20 second respawn than before.
Weapons spawns are apparently fucked up now... They aren't the same for both teams every time... So says someone on Gamebattles forum.
Also, if you look in game, then your achievements are locked. However, you still have them on XBOX live.
Old glitches are still around. Spider infected and stacking hunters.
So far, many players who are competitive or play on gamebattles are pretty upset about this.