I have the HDs on both my Shield and Pro Series. I had them installed on the Shield before I ever walked out of the store, but did shoot the Pro some before putting them on it too. They didn't seem to change the POI from the stock sights.
Both my M&Ps seem to shoot a bit low if you use a classic bulls-eye shooting target picture, balancing the intended point of impact on top of the front sight post. However, if you cover your intended POI they are pretty spot on. With the HD sights, this means just put the big yellow dot (my HDs are the yellow version) right where you want the hole, sort of like you would a laser. Not optimal for bulls-eye shooting, but excellent for self defense, IMO.
For what it's worth, I really like the Trijicon HDs and expect you would too.