I will say from the outset that combat-focused characters will not do as well with this scenario, being much more skill and puzzle focused.
I ran this for a 4-player table, with a ranger, paladin, inquisitor, and bard, all first level. While the bard was really the only one that fit "well" with this scenario, as a group they did well, especially with the supplemental gear given at the beginning of the scenario.
As GM, I had to read through it twice to really get a solid handle on everything, but it wasn't hard to prepare by any means; I just had to be very organized. ;)
Ran this at the 6-7 subtier, with a very mixed party.
I really enjoyed the RP aspects as the GM. Ignizi and Riddywhipple both have very unique and fun personalities, which made for a more engaging story. The other researchers with Ignizi didn't have as strong voices, but you can get them from the description boxes. The layered development of Riddywhipple through the scenario was a very good idea. The story was good, and the roleplaying was strong.
The combats were good as well. Even with a balanced 7-PC party, there weren't any cakewalk encounters for our group. (Optional encounter was skipped for time.) The final battle almost saw two deaths, but situational tactics kept the PC's alive.
My big problems for this mod do come in the combats, and it's only for the GM's running the game. First, the maps given for the second and third encounters (and the optional as well) are near useless. Some markings would have been very helpful on these maps for where Riddywhipple's stuff was, where the pegasi are supposed to be, where the players are coming from, etc., rather than just making a judgment call on where everything is. I completely RP'd Riddywhipple's "map" because of this. Second, while a lot of the creatures encountered are unique and fun to play, they require the GM to have three of four different books to run everything, which many GMs may not have. Also, I had to keep jumping between resources to keep up with the templates on top of the creatures, on top of the tactics in the scenario. This was VERY annoying. One place for everything would be SO helpful. Luckily I had just enough time this week to prep it all, but it's a lot to deal with. Simplify, please!
Even with the issues I have, those are all GM-technical stuff, and the story and roleplaying were strong enough to cover over the issues. Still 4 stars; I enjoyed running it, and will probably play it myself soon.