You might recollect that our recent verdict on Valve's mini co-op shooter Alien Swarm concluded that the game would have been improved somewhat if it utilised the same kind of AI director routines that make the Left 4 Dead games so interesting to play. Well, soon it will do so. Steam News reports: "...we've added "Onslaught" mode, which introduces an AI Director that dynamically generates swarms of aliens based on several factors, such as the squad's stress level. Onslaught works with any difficulty setting and ensures no mission plays the same way twice."
So hurrah for that.