I will use a tension meter when I am dealing with less familiar components or when I want to get nerdy and check for spoke elongation... I have also built and taken apart wheels so I could measure the spokes after tensioning to see how much different types of spokes stretch.

I could build a dozen wheels and you could put your tension meter to work and you'd find that they'd all be within working tolerances... tension meters have not been around forever (and lots of wheels have been built without them) when you do it professionally you develop better senses than those who do this infrequently or as a hobby. If you have read Brandt's treatise on wheelbuilding you would know there are other ways to check spoke tension without a tensionometer.

I was once challenged to build a wheel with my eyes closed... it came out to be 5 by 5 (.005 tolerance) and has been run hard for the past three years and is still 5 x 5.

I also did this because I have a friend who is blind and wants to learn how to build wheels... she will probably do very well at this.