I agree with the last post except... (I don't think we need spoilers?)
What did Lee hope to achieve anyway? The CO2 trick was unlikely to achieve anything more than to shorten the negotiations. He should have bided his time hiding until an opportunity arose. The gunman did not seem to be aware of the wall panel, though Ellen would probably have been unable to lie.
Kara was exposed by Ellen, not the hidden guns, but there did not seem to be a plan to her entry. If they had refused to leave the door open what then?
I see this episode as a way of writing out Billy, and renewing that business about Kara and Zak Adama that has been largely forgotten. As if she doesn't suffer enough angst already!
One other thing though, we discussed before about whether Ellen is a Cylon or just stupid. I'm still not sure now given that she blew Kara's cover and announced to everyone that she was the wife of Galactica's XO.