Hi David Goldstein,
It's fair to say few people use pH meters. I don't use one either, but I won't say it is irrelevant. It is relevant. pH is a variable you can easily measure. And by keeping notes you can keep a variable "in control". That's great. If you have a problem, and everyone has problems, you can check your notes to see if your pH was "wrong" that day. Not too many of us can verify that.
For a specific example, I occasionally get pinholes in my negatives. When I do, the first thing I do is check the bellows and Grafmatics for dust.
It would be cool to rule out whether my stop bath was too acid.