Legally it depends on the state you live in to a large extent, texas and arizona at least (probably more states i am not aware of) allow you to shoot trespassers on your property, they don't need to make it into your home. I think personally if you feel compelled to shoot someone in your home that response is based on a fear for your safety (aside from a few nut jobs who may find it a fun distraction from their gun cleaning sessions, "sweet, free target practice") and thus calling it self defense in court seems reasonable. As a gun owner I would shoot without warning if I awoke to someone in my house, guess I would have to let the courts decide if it was lawful or not... repercussions would not be something I would stop to consider.
Don't try to harm my family in my home if you are not prepared to die trying. And yes, I am technically insane, but not awful, and not dumb enough to believe criminals should have more rights than myself.