there are plenty of people who use it and plenty of examples of work created with it, here on apug or elsewhere ...
caffenol can be made with relatively benign household ingredients
or those found in a grocery store ..
the chemicals are not nasty and toxic like most other developers
the developer ingredients last a long time both dry and mixed
caffenol can be used as a deep tank, replenished, or one shot developer
it can be used as a print or film developer,
it has no trouble processing a variety of iso films in the same batch
for the same time
Blue Monkey -
if you want to make caffenol with just caffic acid
there are lots of suppliers worldwide and it is about 1-2$ a kg
but there might be other ingredients in the coffee that add to the developer
and make it do what it does ... so your results might not be the same ...