Like many others on WickedFire, I am a legal CCW permit holder. Since the tragedy in Aurora, I've spent a lot of time thinking about what I would have done in the same situation.
My response would be dictated by who I'm with. As a father and husband, my primary responsibility is my family. I am NOT going to play cowboy with my children's lives. I would not engage an individual unless backed into a corner and it was necessary to protect my immediate family. If I am able to get them to safety without shooting in a dark and smokey theater, I sure as hell will, and feel bad about the dead later.
Sorry if I'm not the Navy SEAL, or SWAT operator like most here are.