I ran this one for a high tier group of 6, with several well-optimised characters, and a level 1 and level 2 character included. The opponents were a good challenge, even for the optimised characters, and the situations added danger and tension. Bravo.
On top of that - I have not had so much fun running a PFS scenario since the Night March of Kalkimedes. I applaud everything that was done in this scenario, and look forward to more in this vein. My players were laughing the whole way through.
I ran this over the weekend, and the reactions were very mixed.
As others have reported, several parts of this scenario were very challenging, even before adding in hard mode. However, they were challenging in ways that basically just annoyed most of the party. The challenges essentially prevented several characters from participating in much of the scenario. The challenge level was also quite uneven - half of the encounters were close to a TPK for our group, and the other half were a walk in the park. On the upside, at least one of my players was on the edge of his seat for most of one of the difficult encounters. This was actually good to see.
The length of the scenario, like many other higher-level scenarios, is also towards the top end of the scale. I neglected to cut out the optional encounter, and my group finished in about 5 and a half hours.