Quoted from ForceFlow:
Thermal pads were used at one point in the late 90s and early 2000s. There was some debate back then about which was better (pads vs paste). Although, I don't remember thermal pads turning gooey like that. They mostly seemed to dry out.
Personally, I prefer ceramique paste, rather than artic silver. It's not electrically conductive, so if you happen to get it somewhere, it won't short out anything.
Thanks for the input. I used arctic silver because I had it available, but just remembered I also have some other white thermal paste stuff that's been used on transistors in monitor chassis. Maybe that's similar and I didn't even think about using it on a CPU cooler