Firefall isn't being marketed as a traditional MMO, and in fact there aren't many traditional MMO staples in this Red 5 Studios creation. For instance, the class system is series of battleframes. These are armor sets that any player can wear, and they define what role he plays in a group.
Another way Firefall is attempting to carve its own gaming niche is found in the art style behind this third-person shooter. Art Lead Adam McMahon takes a few moments in the latest Firefall dev blog to talk about the evolution of the battleframe design. Some of the original designs for the battleframes conjured up scenes from Alien or Starship Troopers. But the art team quickly realized that it was "making a game for the global market," and therefore, as McMahon explains, "the art needs to be special and it needs to appeal to that broad audience." At that point, the design took a totally different direction and eventually became the look you see in the promo art now and you will see in the game.
If you'd like to read more about how McMahon and the Firefall team inspired the look of the game, be sure to read the whole developer diary. While you're there, take a moment to sign up for the beta.