Its really effective as a home defense gun the way it sits right now.
On my G21 I am looking to put a surefire light and some good night sights to make it a little better to see in the dark at night. As far as putting a light trigger pull, I personally would put a 1,000 rounds threw the gun first cause 1.) the trigger pull will become a little lighter the more you use it and 2.) You will get to know the trigger pull really well to the point were you don't need a lighter trigger pull. You will earn to pick up the "slack" first, then a centimeter further and BANG.
Just my two cents.