Bow quivers vary a lot in size and weight, and shouldn't all be lumped together. You may not like a heavier bow quiver on your bow, but that doesn't mean you wouldn't like a lighter weight 4 arrow bow quiver.
There are bow quivers that will definitely alter how the bow shoots and require retuning the bow. Then there are those that won't change how it shoots, or won't change it sufficiently to where it's noticeable. I have tested (and had others to test in order to confirm) a number of other competitive quivers in trying to determine the extent to which they affect the performance of the bow. The weight of the bow quiver, how it fastens, distance from the limbs, and a variety of other things all come into play.
We get lots of responses from those who say our (EFA) quivers actually quieten their bows. Many of them say that they can't tell that it's on the bow.
Again, don't put all bow quivers in the same catagory. There are those of you who want to shoot 6 or more arrows, and I don't think we'll ever make that quiver. However, when it comes to 3, 4, or 5 arrow quivers, we make them in more sizes, stitch styles, and colors then anyone else. We also make them in limb wrap, limb bolt, and side mount attachment systems.
Our motto is "Travel Light with Eagle's Flight".