Well I think we're all in agreement in reality. Truth be told, I just think it'll be interesting to know roughly the exposure requirements and compare it to say, holography. (that's what led me to mJ/cm² in the first place)
Also, we can say, well Vaughn's tissue requires 250 mJ/cm², and Loris' only requires 175... and ask why is that? Right now our only option is to say, well, I expose it from for 20 minutes from 3 feet away from 24 black-lights under a contact frame with 1/4" soda-lime glass and the relative humidity is always 60% and behind the bulbs I've sprayed Krylon's metallic luster paint which has a reflectance of about....
So, I just want to see what a little regularity might bring to the understanding of carbon and other processes. And if people ever take aims to increase sensitivity, we'll need to have a benchmark.
Ultimately though, like Bill says, being able to step outside and get in the ballpark is probably the most useful thing you could do with one of these meters.