Thanks GF for the kind words. I've been around the block a few times - sad part is I'm starting to look it!
The other "new" gas possibility for auto A/C is R-32. It, too, is slightly flammable - which has kept it out of the American market for refrigerant use in pure form. Europe is using it, and early indications are promising. But the flammability rules preclude its use here - which is why the manufacturers and enviros are pressuring the EPA to change their rules a little to permit a "slightly" flammable gas.
Personally, I am leary of anything flammable in an AC. In the old old days ammonia was the main refrigerant, and one of the main reasons it was replaced (with chlorinated hydrocarbons) was because of safety - as it was flammable! So now we're coming full circle and pushing for a flammable (albeit slightly) gas?
People have said, "It's flammable - so what? There's gasoline in the car, and it's flammable!". Well, with the fuel it's outside of the passenger compartment. With AC, part of the system (i.e the evaporator) is INSIDE the passenger compartment. In a crash a leak in that coil could let flammable freon escape into the area where the people are. Not so sure the phrase "slightly flammable" is gonna be OK with people in that scenario.