Today I had to measure a couple of courses - not for certification, just to ascertain the length, so the organizers could decide among the options as to which route they will choose to be certified.
I jumped in both feet and used my Protegé 9.0. One bonus was when one of the courses came up short, I simply went back to the last mile mark, zeroed it out, and rode an alternate route to the requisite finish.
What I find takes extra time (and creates some degree of uncertainty and worry in my mind) is when calibrating and then doing subsequent calculations.
I've got my rim marked off in fractions of .125/revolution. Each spoke is about .025/revolution (a bit more, actually). So, when I calibrate, I'll record a figure like "152.125 + 1 spoke" or "152.5 - 2 spokes." Then I'll do the math when I'm figuring out the constant, but I wonder if such "guesstimation" is being extrapolated in the measurement itself.
When I use the J/O Counter, the toughest judgement call I have to make is whether it's a full or half count. For right now, that seems more reassuring to me.