Depends on what you're after. I like my longbow light and quick for hunting, but when shooting targets extra weight seems to help.
I quit using bow quivers when I learned through bare-shafting that a bow quiver changes spine requirements. The added weight slows the reaction of the bow during the shot, so the arrow has to be weaker to clear the riser. The riser moves to the side a bit when you shoot because of paradox, and the heavier bow is slower to move.
I also don't like trying to get through brush with one on my bow. My quiver hangs in the middle of my back, out of the way but accessible.