Overlay is a giant sticker used to replace the art. Check out this ebay listing for a Bally Kiss overlay to get an idea on what it is and what installation would involve...

ebay.com link: KISS Pinball Machine Playfield Overlay UV PRINTED Clear Inserts DIE CUT

I'm working with another local pin guy on 2 Flash Gordon playfield overlays currently and I'm also finishing up a 3rd game with a CPR set. After everything is done I plan on posting a thread comparing all them.

The art looks very acceptable compared to a blown-out playfield. There are plenty of opinions out there both pro and con but the process we are using is to sand playfield down completely flat (re-gluing inserts as well), shoot a couple coats of clear and sanding that completely flat, applying overlay and finishing up with more coats of clear. Afterwards, I plan on carefully drilling out the holes for everything before re-assembly.

The overlays are about $200 - compared to what the reproduction CPR ones fetch if you can find a seller.

If you're also doing the cab and are looking for stencils, I would suggest pinballpimp over twisted pins. I did one cab already with the tp set, and registration was a headache (to put it mildly)

It's not 100% exact nor 100% perfect, but it's definitely better than a blown-out playfield (or one with terrible touch-ups) Sure, CPR would be better (NOS would be preferred), but trying to find NOS or CPR without being overly gouged is not exactly easy these days... and the CPR I have has some slight differences and issues as well.

Die cut I assume? Similar to his advertised High Speed overlay. Not sure who did the KISS overlay, but if Jeff is selling them I'm guessing he is printing them?

This sounds like more of an issue with installation than with the overlay itself. I've done a lot of reading prior to doing this so trying what I think is the best approach for me. If this has issues or doesn't work out we'll change things on the next one.