If you look at my posting history on any CoC site, you'll see that Crack'd & Crook'd Manse is my #1 scenario of all time. There are so many great things about it, and I've probably run it 15-20 times in my gaming career. I've even previously posted some tips
here on running it. Needless to say, this was a great episode for me. Also, as in the episode, here be spoilers
Sorry, this turned out to be a long post.
One thing that wasn't mentioned is that Crack'd & Crook'd Manse was originally written as a tournament scenario for Phantastacon 1984 and then published in the Multiverse magazine (issue 3)*. To me, this means this scenario was originally meant to be played as a one-shot at a con. I bring this up because I think thats where some of its quirks come from. The goal of the scenario was to run it for a bunch of people within a short time period and make it enjoyable. To that extent, I think it succeeds. In a con scenario - especially a tournament one - the players are more likely to go to the house even though in different circumstances they may not (e.g. they were in a long campaign). My own experience mirrors this. The majority of the times I've run this have been at cons, and even with people new to Call of Cthulhu, and it has always succeeded in that respect.
IMO, the brilliance of this scenario is not that its a mythos take on a haunted house, but in how the creature works within the house. Since it moves within the walls of the house, it has agency to avoid the PCs for as long as you want it to. If its early in the scenario and the PCs really want to explore the basement, the creature can move upstairs (with the house moaning and creaking as it does). If its later in the game and the PCs are nowhere near solving it, have it appear and all hell break loose.
I can't think of any other haunted house scenarios that do this. The Dare (my #2 haunted house scenario), The Haunting, and others have the bad guy in a fixed location. Sure the GM can move it if necessary, but not as easily.
This isn't to say that the scenario has its flaws. The civil war ghost red herring has never gotten used in any of the times I've run it. PCs don't always dig up that history, and it seems unusual for it to appear. The same with the "NaCl" scrolled on the mirror. That never really sat well with me. I'm totally stealing the idea of writing the company name instead of salt on the mirror. And the vocal mimicry. I can't remember who thought of that, but wow, thats brilliant. Reminds me of The Ruins
I've got so much more to say on the scenario, but I'll stop here.
In the end, I love this scenario and recommend it for new and old players alike.
Also, loved that you guys did this. Please analyze more scenarios like you did here in the future!
* Source is the original Mansions of Madness book.