It was a good laugh, and nice to play something that has a single mindedness (Forward!). We decided my objective was to kill as many Space Marines as possible while the Marines had to kill my synapse creatures. My units of small creatures (gaunts) would respawn from my table edge when a whole unit of them was lost. The Marines started with some units on the table and the rest deep striking in (having drawn the nids into a trap).
The game ended with a good few marines and nids dead. We all agreed it was a fun game, even without using points and proper objectives.