Release date: September 18th
Ok, first this game is being released on my birthday so I must get it.
Borderlands 1 was a point of contention for gamers. In general people really liked it but for some there were issues that were too glaring to forgive. I think the most frustrating problem was those pesky NAT errors in multiplayer, making it impossible to play with friends. Gameplay-wise, the guns didn't live up the promise of infinite and crazy weapons, and the leveling system made playing pick up games with friends all but impossible. However, as a whole I really really enjoyed the game and am looking forward to the second coming.
Some key notes about Borderlands 2
It will use steamworks
It is a lot more colorful
NPCs seem to interact more with the world and the player
Guns seem to adhere more to the promises of Borderlands 1 with early reports being very positive
Split screen coop
Some other stuff from wikipedia:
RockPaperShotgun just posted a hands on which you can read here:New features include a more expansive and customizable weapons system, reworked four-seat drift-able vehicles and vehicle physics elements, and dynamic quest systems. For example, taking too much time to save a friend in a quest may result in their death and the failure of the quest, which will affect the story as the player progresses. Technically, the game world will be all connected, rather than loadable levels for each region, allowing accurate viewing of the entire world from a given point rather than the first game's premade "Skybox".
In addition, the AI system has been reworked for the game. Non-enemies will populate the game world more often and will travel around different locations depending on the time. Enemy AI will encourage teamwork, such as flanking, as well as taking cover when wounded, though lower level enemies like Psychos will still embrace the mentality of, "Wow that's a gun! I want my face in front of it," according to Gearbox VP Steve Gibson. Shooting enemies will stun or cripple them depending on where they are shot. For a change, enemies will be intelligent enough to climb and traverse difficult terrain to pursue the player. Enemies will also be able to interact with each other. For example, certain enemies can heal their teammates, boost their shields for defense, or use them as shields to protect themselves.
So yeah, I'm stoked. Hope this is everything Borderlands 1 should have been plus a bucket of kittens.