1. The first encounter took a really long time. Invisibility + confusion + memory lapse + teleport + difficult environment making lots of spells impossible to use = dragging out the fight. The first encounter was, in my humble opinion, the weakest part of the scenario because of the time it took (and I didn't even use some options like summoning another devil!) I would recommend doing a few shenannigans at first and then just attack with the baddies to get the fight over with.
2. New mechanics/subsystem takes time to explain to the players: research, wild magic, impossible feats in the dreamscape, etc. This was also a factor timewise.
3. I REALLY liked the "secrets" part of the scenario, but I am not sure how PFS does it justice, especially if you play with people for the first time. When I played it, most players were like "Who cares about the fact that you're a former convict and you assumed the identity of a pathfinder who just died". My backstory/secret fell flat. When I GMed it, some of the players had really cool secrets, most characters "denied" what the others could see. With a more stable group and a more time to spare, it think it'd make it more interesting.
4. Prep-wise, there was a lot of new mechanics to learn, new occult options, etc. which made it harder than the standard scenario. The content found on PFSPREP is AMAZING! I'd say it is mandatory is visit the site before GMing this one to cut down on prep time (especially with 2 unique maps - which should be prepared in advance and not drawn on the spot to save some time).
5. My group probably had an average charisma score of 14-16 (paladin, halflings, gnome, sorcerer!) so it was a bit easier in the dreamscape. I've heard of a group with lots of charisma dump stats so the last fight was really quick and brutal. I LOVE the fact that it shows how bad dump stats can be. Good job on that one!
6. Storywise, my players absolutely LOVED it! 322 is a really interesting character and some many players were in admiration of her backstory (I was as a GM as well!) Excellent job with the story. I could see how it would bore some players that aren't interested in anything else but killing stuff.
7. The investigator in my group decimated the research part of the scenario (like Lamplighter said). The friendly rivalry didn't happen, because of lack of time and also because the players semeed mostly happy with succeeding as a group. While some knowledgable characters wanted to be more useful, it helped me cut down on research time, which helped run the scenario faster.
8. Fight-wise, I wasn't able to properly run the last fight because of the time crunch. I could see how ill-omen + phantasmal killer would be an interesting combo! The charisma damage can be VERY lethal if you concentrate your attacks on individual players. The aftermath of the fight was done in like 2 minutes (unfortunately). I wish I had more time to let the players talk to the Night Hag. This is supposed to be the highlight of the scenario in my opinion. Make sure you keep some time to run the conversation properly and to report back to Shaine after.
