Is extremely accurate "VTA" adjustment necessary?

of course any adjustment to your sytem should result in some improvement of sound or mechanical function.
what is the purpose vta adjustment? some say it is to duplicate the angle of the cutting head. If you accomplish that you have got it right. other's adjust vta for the "best sound". the latter of course is a subjective determination and by definition must be assessed by ear. However, I contend the actual arm height adjustments must be measured either by using the tonearm manufacturers built in device, a la wheaton triplanar, or some other extremely accurate measuring device. Only then can you be sure of what you are doing and to be able to repeat your efforts. the more sticky issue is duplicating the angle of the original cutting head, assuming one could determine what that is. Of course you would need some fancy protractor to adjust your tonearm to achieve that angle.
then of course what do you when your golden ears tell you that some other vta produces "better sound"? I don't know.
in a perfect world we would hope that the angle of the original cutting head and the "sweet spot" as determined by our golden ears would be the same. not likley.

Addressing the issue of "golden ears" here, for a minute, I'd suggest that everyone has "golden ears", and by this I mean that everyone has an idea of what they think it the best sound performance in their own systems.

So, in this respect, each person can decide which settings are most pleasing to them. There is no "perfection", so everything is some kind of compromise. Even with the most accurate measuring equipment, there is an accuracy tolerance which will allow error, even if small. Some might say that the ears are flawed as measuring devices. Others would say they are the most meaningful measuring device for audio systems.

Regardless of your measurement techniques, getting the audible results that you desire is the end goal. I know that opinions vary greatly on this issue, and there are some who don't want to accept any compromise, while some will easily accept compromise for ease of use.

To each his own. If measuring everything precisely with meters and gauges makes your experience more satisfying, then by all means, go to it. If just simple "set it and forget it" adjustments make you feel better, then that's fine too. It is all in what you want as a listener.

I think many of the above posts gave excellent information for people who are trying to maximize the performance of their systems.

what is the purpose vta adjustment? some say it is to duplicate the angle of the cutting head. If you accomplish that you have got it right. other's adjust vta for the "best sound".

Your two "alternatives" do not represent different purposes. They represent different techniques for achieving the same purpose.

The purpose of our hobby for me is maximising musical enjoyment in my home. I set arm height for best sound, since that maximizes enjoyment, but isn't it likely that I'm also matching stylus angles, within the limits of my hearing of course?

I listen for and hear certain specific things while adjusting arm height, so it's reasonable to think there's a consistent mechanical explanation. (That hypothesis is the topic of this thread.) My current unproven belief, until a better explanation comes along, is simply that I'm using "best sound" as a proxy for matching playback stylus angle to cutting stylus angle.

Whether I'm matching as well as one could with a scope or other measuring device is of little practical significance. Optimum arm height varies from record to record. Having to drag out a scope to calculate arm height for every record would be wildly impractical for home listening. I can adjust arm height to my satisfaction while listening to and enjoying the music. As Rushton said, using a scope to set azimuth is preferable. This is because, unlike arm height, azimuth does not change from record to record. Use the scope once and forget it until you change cartridge or arm.

If I were playing LPs for archival or commercial transcription to digital I would take the time to get SRA technically "perfect". But for home listening that seems over the top to me.

In several instances where I have had others around while seeking to set the VTA, there has been total agreement. I do not think it is so totally subjective as TWL suggests. But I totally agree with him that it is a subjective experience, that you say, "Aha, that is it."

Dougdeacon, yes for most arms the VTA has to be a compromise setting. I once had the Wheaton arm which has an easy VTA adjustment with an easy reproducted marked scale. I did mark many albums as to where they should be set. One cannot do this with the Schroeder so I use the best overall setting.

ok, here's what you want with respect to vta. the stylus manufacturer has decided stylus stip shape. maybe spherical, eliptical, micro line,etc. your goal is to have that stylus tip rest in the grove exactly as the manufacutrer intended. thus you will achieve maximum contact of the stylus as was intended. thus you need to have the cartridge aligned perfectly in all planes. Also correct antiskating force is essential.
If vta is off it will cause the tip to tilt forward or backward giving less than optimum contact. Take a good record get the vta right. tonearm parrallel to the record surface while stylus is resting in the grove with correct tracking force and anti skating force. then you need only measure the width of each record and adjust tonearm height for the difference. don't measure the thickness from the lip of the record but from the middle part of the record.