In way to many places it is not--too many places require that you retreat, and they treat you as the guilty person and you must prove that you were in fear for your life. Most Castle Doctrine laws put the assumption of innocence back on you and the burden on the prosecutors.
My unfair advantage has decreased significantly, but it's still here.
My wife isn't necessarily able to evade attack (just had a new hip and new knee put in) or to defend herself (smart hand still out of commission from rotator cuff work, and will permanently lose range of motion and some strength.) Therefore, it's not just MY life at stake.
When her mother was still kicking, her condition was such that I'd have actually gotten in more trouble for fleeing (and leaving her to her own devices) than I would have in handling the threat directly. "Murder by depraved indifference," I believe it was called (falls under Murder Two or Murder Three - I don't recall which offhand. But, it's definitely considered "Murder" and not "Manslaughter.")
The core premise of Castle Doctrine is that, when you face an intruder in your home, it is reasonable to assume that his intentions are nefarious and that he poses a threat to your safety and well-being - and that you are entitled to respond in kind. You can still get knocked off for "excessive use of force" or somesuch - so you'd better make sure it's a lethal threat to your person (the seven-yard rule applies, if he's not empty-handed,) so you have a
far better chance of winning the case in a Castle Doctrine state.
The only remaining problem is that, if the shoot is ruled "just" (read: it passes the "reasonable man" test and is perfectly justified/justifiable,) it should close the door for civil action as well. That door is still open, and it causes trouble (you can be found to have fired in self-defense, and the silly bastid can still sue you for punitive damages. Which I find awfully asinine - there's another principle that goes by "But for your actions..." Ex: If you have a pool and put a fence about it and secure it, then some damnfool climbs over the fence and drowns, his folks/family/whatever
can sue you civilly - but you're likely to come out. "But for your actions" applies - in this case, it can be read as: "If the victim hadn't climbed that fence, he would not have drowned. The victim put himself in that position, no-one forced him.")