Reinhold, a photographer from Heidelberg, Germany, has started an excellent english blog about Caffenol - and his results are just amazing. Some people confirm his findings, including a range of 13 - 14 f-stops with Fuji Acros. He even shows photos with Acros@1600 ASA.
This is a great blog. I have followed its recipe for the Caffenol C-M
It IS a great blog, have a close look at the recipe for Caffenol C-L
I've used the Caffenol-C-H recipe. Reinhold's site is brilliant. Treating Caffenol professionally may detract from the magic of a Home brew developer for some, for me though its just what the doctor ordered. Getting consistent results is not a bad thing in my book. I've been so brash as to blog my own experiences with TMX and TMY-2 here: http://on-your-kitchen-worktop.blogspot.com