Most of the overlays are rubbish and because they are not licensed, they are often crap. I've seen KISS and Playboy overlays and they looked disgusting. At least the seller stipulates that there is an overlay installed. He has a few other Bally classics from this era in his garage, and he lives around 5 minutes from my place - but I've never heard of him.
I've put my name down for a Mata Hari Playfield from CPR and I'll wait for their backglass as well. This is a classic game that deserves the full treatment.