It's been on the market for some time. The instructions scare me when they say to introduce AIR into the system before charging. That should not be necessary, and if it does help, it is only because your system is not designed for hydrocarbons. I'll stick with R134a.

EPA regulations carry the force of law. Note that it is against EPA regulations to replace R12 (or any other ozone-depleting refrigerant) with any hydrocarbon. So you really should not call this a "drop in" for R12.