There was a guy on the LeSabre board that used it. Expensive stuff at $6 a bottle...
But it supposedly cools, lubricates, and keeps parts cleaner than earlier versions of ATF. Keep in mind the 4t60 (AKA 440-T4) used in the LeSabre T Type was designed with dextron-mercon II in mind which doesn't even exist anymore since technology in fluids has advanced.
Anyway, the guy that tried it said he felt much smoother shifts and quicker acceleration. Granted he changed out old fluid, but I don't think the "old" fluid was particularly bad.
Granted there is no way to actually proove seat of the pants results without a dyno.
Personally, I probably wouldn't spring the extra cost per bottle for it. I did buy one not too long ago just to see what it was like and it seemed to flow just a tiny bit thicker than Dex/Merc III but otherwise everything else seemed to be the same.
I guess my point is that it *might* help, but not enough to bother with in an ordinary trans on an ordinary driver car designed with the older stuff in mind anyway.
RIPBC... Off to bigger and better things