Indexing can assist in some cases, but not all that often IMO. I'd say 9 out of 10 times it is not necessary. It can be effective on both ends of the arrow for aligning heads with vanes and nocks with dynamic spine, and sometimes a combination of both. Again, I rarely find it helps, but there are those instances when it can.

If you like Muzzy heads, and think indexing is something that is of help to you, take a look at Innerloc's new BAT system heads. One is called a Carbon Tuner and the other is the Falcon. They have special ferrules that are machined to allow you to turn the head and tighten them down whereever you want so they can be indexed without having to reglue inserts or refletch arrows.