This is different on too man levels to say that it's like L4D. Only things similar: 4 characters (not terribly an unoriginal idea though, since consoles use 4 controllers) and zombies. And the teddy bear thing. But where else is it an L4D ripoff? Every zombie game has in ways ripped off one game or another, no zombie game is truly original because of the whole "zombie lore" idea. They may have changed one or two aspects of their game to give it the L4D feel, but otherwise it was probably their creation as I don't see similarities in the core gameplay.
Personally I think it will be more fun than L4D, and we may have some fanatics who will shoot me down on this, but it's too difficult to play a full game of L4D, even with friends. And bots are definitely no fun. And in this version, it will be more about just shooting the z's until your fingers are sore, and once they get sore you can get up and quit without any remorse for leaving your friends.
If it rips off anything, it's moreso of Alien Shooter where you have to kill hundred and hundreds of aliens.
So stop rewording the person right above you when they say knockoff, and look at the game. It's not an FPS, it's not a "Point A to Point B" race of death, it uses different guns, and it will have 55 arenas to play in. Of course L4D is going to be influential because of it's success, but every zombie game that comes out after this isn't going to be ripping off L4D.