Its been almost 2 years now that I've been running ES-12a and the A/C is still running great.
I ordered a second kit for the white MR2 that I picked up recently and it looks like the enviro-safe kit now comes with a black light along with a thermometer. This round I ordered the kit that included the gauge and valve that connects directly to the r12 fitting on the car so it doesn't require an adapter. My first kit had a 134a end on the gauge and came with adapter fittings that screwed onto the cars r12 port.
For $50 dollars shipped it can't be beat:
eBay Motors: R-12/R-134a Enviro-Safe Alternate A/C Recharge Kit-R12 (item 390020145758 end time Feb-26-09 04:27:06 PST)