The Official PlayStation Blog had a live Q&A chat with Naughty Dog’s Creative Director Amy Hennig and Co-President Evan Wells. Here’s what we know about Uncharted 2: Among Thieves based on that chat:

• The single player campaign is going to be longer than Uncharted: Drake’s Fortune.
• Uncharted 2 will feature over 90 minutes of cinematic alone.
• Inspiration for both Uncharted games came from books, comics, movies, etc.
• The final list of Trophies is still being finalized and it looks a few MP trophies will be included.
• Developing the multiplayer experience helped Naughty Dog to improve and enhance the single player experience.
• An official release date will be announced very soon.
• Local multiplayer is not supported.
• The combat, enemy system and hand to hand melee has been improved.
• Enemies has classes. The lightest classes of enemy will allow you to perform hand to hand combat much the same way it was in the original game, but the medium classes enemies will counter your attacks requiring you to dodge before you can finish them off. Then the heaviest class of enemies won’t let you melee them at all.
• Naughty Dog and Arad Productions have been working on the Uncharted movie for the last year-and-a-half or so.
• Another multiplayer demo will be available before the game hits shelves – for a wider group this time.
• There are several more multiplayer modes that will be announced in the future  – Several more competitive modes and at least 2 more cooperative modes. There will also be variations on all the competitive modes that will focus on specific kinds of weapons.
• A special Cinema mode will allow players to play back any of their matches and view it from ANY angle. Players will be able to upload those recordings and screenshots.
• There’s a skill rating system in order to match players against one another to ensure that the matches are close
• There’s a wider variety of environments in Uncharted 2. Urban areas, ancient temples, jungle swamps and snowy and icy locales. Nate’s journey takes him from Turkey to Borneo, up to Nepal and into Tibet and the Himalayas.
• Uncharted 2 will be a stand alone experience. You don’t have to play the first one in order to enjoy the second.
• Both Sullivan and Elena return in this game.
• There’s a similar amount of puzzles in Uncharted 2 as in Uncharted 1, but there’s also more problem-solving in the levels – figuring out how to navigate the environments, and what’s the best approach to different combat set-ups. A journal will be available to assist with puzzle-solving.
• Drake and the enemies will leave footprints in the snow with 3D clumps that build up around their feet.
• The sixaxis controls are optional, but they really enhance the grenade mechanics now that we’ve got a dedicated button for it.