I'm very fortunate to live just an hour's drive from Pinball Decals (PDI), so tonight I drove down and added 8 more sheets of PDI glass to the one I bought last year for Metallica. The quality is excellent on these - I didn't have to clean them at all, just unwrapped them and installed them with a pair of cotton gloves. I can also tell you that the owners of this business are really nice people. They're the kind of people you wish your neighbors were like.
It's not hard to justify this mod, especially for older pins with great artwork. But I'm not going to worry about justifying it. Next month, I'll hit 20 years with the same company, and I wanted to celebrate a little. It was a lot cheaper than a new pin. Having the PDI glass on Metallica for a year made it hard to wait. The difference is very noticeable.