With regards to waiting until the gun is pulled out, the police are generally required to do this before they can legally kill someone. I wouldn't think it would make sense to allow private citizens more leeway in self-defense then it would the police.
Of course, I would entirely agree: in public areas, one should have to wait until a gun is pulled out. However, different standards should apply when one's own home has been broken into.
In general, when someone breaks into your property, I would think it reasonable for you to assume that he intends to cause harm to you, even though no gun may be in sight.
Also, police officers are given, at their police academy many, many hours of training in firearm instruction and how to handle the stress of being in life threatening situations. Regular people don't have such training.