Came back from a business trip and had my copy waiting for me. I wrote a review here:
http://www.enworld.org/forum/showthread.php?658407-Stranger-Things-Dungeons-amp-Dragons-Starter-Set
In short, some collectors will not be thrilled. Also,
Lost Mines of Phandelver is a far superior adventure than
Hunt for the Thessalhydra, but I think that Thessalhydra is much easier to prep for and run for younger, new players.
This is a good choice for younger fans of Stranger Things who want to try out D&D. It is an okay choice for collectors. I'm sure many completionists or uber Stranger Things fans will get it, just to have it.
I got it partly just to have it as a fan of both Stranger Things and D&D, but also for my 9-year-old son to run. He's played D&D both as a player and as a DM (with me helping out with the rules) and when younger played Hero Kids and No Thank You, Evil! So he's not new to TTRPGs. But Phandelver is still a bit much for him to run. Thessalhyra, on the other hand, is very doable for him. Also, there is a bit more replayability in that the random-dungeon generation rules can be used to run some games on the fly. Moreover, it is easy for him to look at the crude, hand-drawn maps (supposedly created by the Mike Wheeler, a character from the TV show who was the group's DM), and make up with his own dungeons.
I expect this set to get a lot of hate and I'm already seeing it in various comments and reviews on different sites. Most seem to be from disappointed collectors or adult players who already are experienced D&D players. I'll be more interested in the opinions of young, new players. If it brings more young players into the game, it will see this as a success.