The Fallout: New Vegas patch meant to lead into the Honest Hearts DLC is available now for the PC, with PS3 and Xbox 360 versions expected to hit soon.
The Fallout: New Vegas version 1.3 patch is a surprisingly comprehensive update that adds numerous optimization and stability improvements and also overhauls just about every weapon in the game, making both guns and energy weapons more accurate and harder-hitting. Explosives have also been changed: dynamite now has a larger explosion radius, while grenades of all sorts have increased damage and the missile launcher and Fat Man have an improved zoom field of view and accuracy.
I'm not sure why there was a need to ratchet up the effectiveness of firearms since the game wasn't exactly the world's toughest shooter-RPG to begin with, but from the look of things this patch will have you killing with greater ease than ever before. Two perks have also been affected: "Splash Damage" now functions properly and "The Professional" now includes the 10mm pistol and SMG.
A full list of changes can be found on Steam, where the 1.3 patch is available now; the Xbox 360 and PlayStation 3 versions are expected to be out soon, followed presumably reasonably closely by the next New Vegas DLC release, Honest Hearts.