I think a lot of people that are freaking out about this are inexperienced, with due respect. Video games go through different stages of developement -- alpha/beta etc. I think a lot of game developers shy away from showing off their game too early for just this reason; they do not want people to see the unfinished product, when they know changes will still be made.
I get what you're saying here, but the progression from alpha/beta material to final product is usually an increase in quality not a decrease. In this case the story they showed was cut and is almost non-existent in the game. The graphics are lower quality and more stylized which even if that decision was made due to consoles/hardware limitations, they really shouldn't be so far off when said footage is two years old. The game's release date was pushed back so they could make a higher quality game yet we still get a product that feels a little haphazard/hastily put together (using same footage of aquarium victors taking the boat and just switching out sec/res characters etc.) and repetitive (single primary objectives with reoccurring bottlenecks and little reason to go off exploring a map).
Now don't take this the wrong way, cause I love Brink, I really do. But as someone who not only works in the industry but has been following this game since it was announced, I'm a little disappointed in the final product. I'm really hoping the free DLC will make up for some of its shortcomings and revitalize the game, cause it is still a great idea and a decent game to pass the time with friends but if it completely dies out it'll be because of Splash Damage's poor execution and inability to live up to the expectations they set.