GT9, Glock recommends that the 3.5/4.5-lb connector only be used for recreational shooting, UNLESS it is combined with the NY-1 module which replaces standard trigger spring and brings total pull weight up to six pounds or so.
A lighter than factory spec trigger pull facilitates an umeritorious prosecution or a groundless lawsuit built on the false theory that you shot the attacker accidentally instead of intentionally. There is no such thing as a "justifiable accident."
In-depth discussion can be found here: http://www.glocktalk.com/forums/show....php?t=1259716
Note where the people who have experience dealing with this sort of thing in court come down on the issue.