It has been a year since I posted my thing on ATF+ vs DEX III; figured I would drop by and post an update on things.

One thing I have learned that I did not know when I posted this, is that mixing the fluids can have one unexpected result; it seems that the additives (stabilizers, anti-foam, cleaners, etc) and cause corrosive byproducts when placed under heat and pressure. (I would suspect this was intentional - if I was one of those types to think such things).
In any case this can cause seals to leak (internally and externally).

I'm happy to say however that after a year of running 1/2 (Valvoline) DEX III + B&M Synthetic trick shift, everything still works great.
I really suspect those having problems with adding other than ATF+4 are using store labeled junk (even if it is labeled as ATF+4). If you decide to play with one of these electronic tranny's (fluid wise) I would suggest you understand what we posted and what it means; or leave it alone.