I think the idea is cool but the application hasn't progressed much beyond a gimick to date. From what I saw from the intial Munsters stream, the mini playfield seems to be more involved (VUK, ramp, bash toy, and mult-ball) than others have been in the past. I owned an AC/DC Premium for a while and didn't care for that mini playfield but I'm certainly not against them. The one from Congo is cool I guess but doesn't really add much to the experience. Definitely looking forward to flipping a Munsters Premium or LE to see if that mini playfield is fun...first impression is really positive though.
I'm wondering if we'll see a machine with an interactive backbox again this year like Scared Stiff or T3. I know that machines like Circus Voltaire, NBA Fastbreak, and Big Guns also apply but I personally think that Scared Stiff and T3's backboxes are more interesting.