We'll see where Walking Dead ends up. It should have been a home run, but to date it is not. If Stern comes out with some killer code updates and maybe a few recommended mechanical tweaks (beyond what is required to make the mechs work out of the box, which they've done for the most part) it could be great. Right now it's not.

Metallica Pro is fantastic and I prefer it over the premiums. The art is solid, which is the biggest difference. You're not missing anything with that terribly executed hammer mech. It looks (and is) cheap and is in a terrible position. The drumroll spinners are pretty sweet and it's a bummer they pulled them from the pro, but it's not enough of a difference to make the premium worthwhile.

I'm also not a Metallica fan and have been a Walking Dead fan since long before the show aired, but when it comes to pinball I'd take MET any day over TWD.

More stuff is not necessarily "way better". Is it $1500 better?

You're just drinking the Stern Kool-aid. If people didn't buy into this then every machine would have the premium features, and it wouldn't be an extra $1500 for maybe $50 worth of parts and a person-week's worth of code. Art preference you can argue, I do like the Monsters and MoP art over the Pro.

The p3 is proposing to support an ENTIRE GAME add-on for $2000-ish. What is Heighway's price point on swappable games?

You might not want to post that kind of stuff online unless you already have a quote. The distributors, if they're smart, are reading this thread. If I was quoting something that I knew someone had already made their mind up to buy that day I'd jack up the price a bit. I'm not in sales though, so y'know. Be sure to shop around.