Shooting an intruder or assailant can be very risky.  For one thing, if I heard someone in our home in the wee hours I would first have to be sure it was not one of our own kids or grandkids having come in earlier after we went to bed to spend the nite and raid the ice box.   Also, these days, some police and some judges go hard on people trying to protect life and property, and look for ways to demonstrate that shooting an intruder was not necessary.  Far too many law enforcement people and judges are lacking in understanding of the US Constitution and especially the Second Amendment and/or lacking the integrity to be guided by it.  People have been charged with assault and murder, and even convicted of same for shooting intruders and assailants.  Laws, and more importantly attitudes vary from one state to another and from one community to another. 

A case that occurred here in town some years ago Re. self protection against assault and battery can be reviewed at:
http://video.google.com/videoplay?docid=-9098745409609387546
and at
http://www.crimefilenews.com/2005/12/whatcha-ya-gonna-do-shoot-me-******.html