Quoted from MikeS:

If the Vault edition has the new SPIKE system it will feel and play like a different game. I've put about 7 plays on the new WWE game and can tell you that it doesn't feel or play like a traditional Stern game. The flippers feel completely different. They aren't as strong or snappy as traditional Stern flippers but feel more solid and consistent. At this point I'm not sure if I like them better or worse. The gameplay itself feels more like a 90's WPC game because of the flipper feel but it just felt strange playing a Stern game that didn't have that Stern "feel" to it. I think a lot of people are going to be in for a surprise once they play it. If they build old games using SPIKE it will be interesting to compare and see which feels better and is more fun to play.
As far as Metallica Premium goes it just makes too much sense not to make a Ride the Lightning Premium at some point in the near future. Dirty Donnie still seems to be doing side work with Stern and on good terms so it only makes sense to hire him to do some new side art/translite and sell a bunch more games. For me the current Premium isn't intriguing enough and the LE is too much to justify over getting a HUO Premium but I think a RTL Premium would be the perfect sweet spot for a lot of us collectors. Come on and do it Stern!