It stains the negatives, is more expensive than some normal developers, might have unreliable results with new coffee batches and has a bad, time-consuming workflow - you have to prepare it fresh each time and use it immidieately.
Other than the above it's a cool way to develop photos with everyday ingredients in a pinch. Used it several times, it was fun and worked but [see paragraph 1].
The delta STD (who makes these names) recipie was a slow (13-15min for most films) fine grain developer. Stained negs brown a bit, even with ridiculously excessive rinsing.
