Recently on another forum there has been much talk of the inaccuracies of pH/KH charts.

I've only recently heard of the pH difference method i.e.

test tank water pH
leave sample for 24 hr.
re-test
if the difference is a pH of 1 then that's 30ppm CO2 in the tank

Is it really that simple? No need for KH testing.

Assuming this method works, if we have accurate pH testing then all sounds good.

Are there any flaws to this method?

PS I'm loving VaughnH's dropper method too. I just don't like equipment in the tank.