There was also a tech notes issue described by Leonard Zinn of Velonews and elsewhere, prolonged soaking of chains in simple green can cause microcracks in chains, Wippermanns seem to be the most problematic. I do not like chains breaking.

I have tried the stuff, but use gloves and rinse well. On Chains I think the rinsing part is the big problem, the stuff I think required rubbing with a cloth while rinsing to remove all the "film". I no longer use it.