The Secret Armory of General Knoxx hit Xbox LIVE today. It raises the level cap to 61, adds new vehicles, and new weapons classes.  The storyline follows after the close of the original game adds over 30 new enemy types.

Along with the DLC comes the patch as well (info from Blend Games):

• Invalid weapons or items can no longer be loaded into the game
• Brick’s Centurion class mods now regenerate health correctly
• Brick’s Bombardier class mods now regenerate rockets correctly
• Roland’s Tactician class mods now regenerate shields correctly and display the correct bonus values
• Roland’s Rifleman class mods now apply damage increase to all machine guns
• Certain powerful legendary item names should now be displayed in the appropriate color
• Opening the bank in the Mad Moxxi DLC no longer prevents other players from moving
• Multiple copies of DLC missions can no longer be obtained
• Corrected some incorrect icons in the ammo vendor
• Fixed a crash caused by killing the final boss while zoomed in with a scope
• The “Careful, he bites” achievement should now properly unlock when playing in French
• Added icons to the server browser that indicate which DLCs the server has installed
• The server browser now displays the name of the DLC a server is playing instead of the plot mission
• Adjusted scrolling in menu options in long server lists
• Added a notification if a player attempts to continue a game saved in DLC that is no longer installed
• Fixed DLC notification dialogs that were not closing properly
• Fixed an issue which resulted in corruption in saved games
• Zombie Island achievements now unlock properly in splitscreen

Balance adjustments:

• Chests in New Haven have been adjusted to contain more appropriate loot
• The duration of daze effects has been reduced to 6 seconds, and the amount by which it decreases the speed of enemies and their projectiles has been reduced
• Damage from shock elemental effects has been increased
• Repeater pistol damage has been slightly increased, accuracy slightly decreased

Sniper Rifle critical hit bonus has been increased