I emailed Stoptech regarding this and this is their response:
"We do not consider salt exposure by itself to be an issue with our Street Performance pads. What can cause an issue is not using the pads in a performance manner where they are regularly exposed to elevated temperatures which allow them to maintain an even pad transfer layer. I believe the only reason salt would be considered part on the issue is that it is typically quite difficult to drive in a manner that will bring the pads to their preferred temperature range when the weather is such that salt needs to be put down to prevent the roads from icing over.
It should be noted that our pads are considered performance pads and should be driven in a performance manner to achieve optimal performance. If performance driving will not be regularly engaged in, including activities like autocross, aggressive back roads and light duty track days, then other pads should be chosen that are better suited to more typical driving conditions like our PosiQuiet or OE Formula pads described on our website here:
http://www.centricparts.com/products/brake-friction
Let us know if you have any questions."
So it looks like the OP may just not be driving his car hard enough over the winter months... or maybe did not bed the pads in properly? either way, I think I am going to go with centric (R1) rotors and the stoptech street performance pads....
The link they provided is very useful...