The gameplay is repetitive and story is pretty simple, but I've enjoyed the game for what it offers. Had a lot of fun trying the different snipers and just clearing the map off zombies.
There's also 16 different characters to choose from, 8 of them from the Left 4 Dead series. In my opinion the original survivors are fun in their own right even though they don't say anything.

Beat the game on 4 player co-op on Sniper Elite (Elite) difficulty. Truly Elite.