There's so much going on in this demo that's it's really hard to pick where to begin describing it. I talked to the developers the other day, and they said the purpose of this freebie is to give you as much of the multiplayer game as they can in a reasonably sized file. So, you give Naughty Dog 1.5 GB, and they're giving you four maps, four competitive modes, two co-op modes, the much-hyped cinema mode, the ability to create custom games, access to new skins, about 80 percent of the boosters you'll find in the final game, and so much more.
Sadly, none of the stuff you unlock and none of the cinemas you create will carry over to the retail release of Uncharted 2. Similarly, your multiplayer rank will be wiped when the final game hits stores. However, Uncharted 2 packs a built in Twitter link and it's going to be active in this demo. If you enter in your Twitter username and password, the game will automatically Tweet your special accomplishments.