I am sold on PB since the first time I was talked into a can of it while at a parts store for something totally unrelated. This old counter guy was talking to a customer as I walked up to cash out. He was telling the customer how good the PB was, etc. I decided to try it myself, having not had any especially good results from much of anything else through the years.
One of the first times I used it was on a buddy's Pontiac T/A radiator support. I sprayed a stuck, rusted bolt (battery acid) and walked away. I came back and the bolt turned so easily that I almost hurt myself when I put my weight on the wrench to turn the bolt. I accused the guy of loosening it and not telling me, there was that much of a difference. Using it in the years since then, I know it was no fluke.
My only complaint is the nozzle doesn't take a straw, I always have to root around for an old spray tip w/a straw to replace the PB tip with.
But I've never tried acetone/ATF. I have noticed that acetone eventually screws up spray bottles, though. Maybe mixed w/ATF it wouldn't be so bad. Acetone also evaporated VERY quickly, so if it didn't penetrate within a short time, it's going to be gone leaving just ATF.