I also have had mixed reviews, there are very few products that are the cure all or as good as all the hype (gotta say I am impressed as heck with SPI though) but I have used plenty POR in the past, enough that I will probably be sprouting a extra arm or something due to it being pretty caustic. Most degreasers that have the "slick" feeling left on your hands is just a Phospheric solution, no magic there and most are based on that, right down to purple power etc.
I won't use the POR much anymore but will the engine paint, I had a motor that was painted with it and the machine shop couldn't get it off with there cleaning process. I think sometimes good ol' epoxy primer with a good paint on top is simple and easy to touch up, if it can get powder coated thats what I tend to do as well. sorry to hear your problems though.