I have to start pushing this
test more. It seems as if it provides an answer to one of the most
common brewing forum questions: Why is my FG higher than expected?
Interesting enough, most of the very experienced American home brewers
don't use this test either. Might be that their process is refined
enough that the information given by this test is just redundant. But especially for beginning homebrewers, this test can provide invaluable information regarding the FG that can be expected. Almost as important ad taking an original extract (OG) reading. To many of them are just hung up on the attenuation numbers that are given for the yeasts at White Labs and Wyeast. When I asked them about the procedure that is used to get these numers, they told me that they don't even use a standard wort for all the yeasts.

I
certainly swear by it. How else can you find out if you met your
targeted fermentability during mashing before the beer fermentation is
done. It has become very important to brewing lager beers as they seem
to slow down significantly towards the end with a risk of being to
sweet before going to lagering temps. But even with Ales this test is
useful as it actually allows me to take residual fermentable sugar in
the beer into account when calculating priming sugar additions.