The dark comedy aspect, the performances, and the overall concept. And the guitarist was awesome!
What I didn't like
Some of the one-off jokes were brought back multiple times which weakened the joke the second or even third time around. The show wasn’t quite as tight as it could have been with transitions, dialogue, etc., but I saw a preview, and I think that will be resolved come opening night. Also, this is really nitpicky, but the Dee Snider wig bothered me because it looked so fake compared to the rest of the outfits, wigs, and hairstyles (this shouldn’t affect you going to see the show, though).
My overall impression
While the show might not be so tight yet, it is hilarious, thought-provoking, and surprisingly endearing. The performances are great, and the script is well-written. Once the kinks are fixed, and the show tightens up, it will be a really strong production.