I've completed the finale, all the navmeshes are done and have no errors, the final lighting compiles are done, and the campaign is now playable from the start of map#1 to the finale in map#4.
I'm currently doing a final few playtests and then I'll be able to release a public beta.
The finale has worked out great and isn't remotely like a Left 4 Dead finale you'll have seen before - but I'm not going to spoil the surprise by giving any more details. :)
In the meantime, I've added several new action pics to the media section.