Even the 3.5 version of this scenario had some legitimate challenges, and with the conversion, Subtier 4-5 now has the best challenge of any Season 0 I've seen (Subtier 1-2 looks like it would be a cakewalk now, though, so if you're running this for a home group, consider just using the 3.5 version if you're running Subtier 1-2). It isn't overpowering, but there's a few things that can go very wrong for a party.
A group that is high on Cha and Int casters can be screwed by the mists, which completely incapacitate all spellcasting for those characters. Somehow every time I've played or GMed this one, there's been a sorcerer around who failed his save and got monkeyfied. Fortunately, the module has a clever built-in mechanism for modulating the challenge--if the party starts losing and someone gets KOed, you learn that KOing ends the monkey effect, whereas a curb-stomping party may never learn this depending on how they dealwith the ape scholars. The only trouble, of course, is if the team all dies on the encounter with the first KO. However, you do need to be able to heal off that fight. When I first ran this, it was with a party who were all completely new characters and had no CLW wands. This can be rough in any scenario, so remind the group that they can pay for heals at a temple if necessary.
The other potential trouble can be the vargouilles. When I played this with my monk, he was the only one who made all four Will saves at the higher tier. If he had failed and the vargouilles were played smartly (knock out, then kiss, then wait), we would have had a TPK and several new vargouilles. In general, multiple save or disables coming at once can be pretty tough. Granted, I haven't yet seen this one actually take out the whole party, but do watch out. In general the mod has plenty of save or sucks, but this is the only case where there are so many that have such a dangerous condition.
If you can somehow avoid the ridiculously easy PFRPG version of the 1-2 subtier, consider the rating increased up to 4.

The encounters added to the flavor and theme of the demon-mist-haunted museum, with a good variety of opponents, each themed to one of the museum's exhibits. Several examples include vargouilles masquerading as masks, the taxidermic monsters in the same room that don't come to life (yet), and a ziggurat with a giant gorilla surrounded by monkeys and evil monkey idols hiding in the brush.

This scenario is basically a dungeon crawl. There is one opportunity to talk to a besieged scholar which is essentially the only RP encounter you get unless you count the Venture Captain or Nigel Aldain, who you save at the very end. However, the RP potential of the mist itself boosts this one up to 2.5. Be careful, however, as the mists are clearly portrayed as a negative effect, so you need players who will ham it up despite this fact, as opposed to the sorts of players who don't like to dwell on failures or setbacks.

You get surprisingly-much in this category considering it's just a dungeon crawl in Absalom. While not directly relevant to this particular adventure, the lore on the Blakros Museum itself was rich and evocative enough to spawn several more adventures each off of unanswered questions piqued by the scenario's background text. You also get Anghazan and Mwangi themes. Finally, having Adril Hestram as the VC is useful to build up to the retirement arc. This is a scenario in which the PFS would logically be involved, and the adventure flows together well with no logical inconsistencies except perhaps how the giant crocodile fit itself up there.

This category exists for things that just make the characters call out "That's awesome!" On the other side, it includes things that make them groan, but I've named the category after the positive side of the aspect. The flavor oozing out of this scenario is what makes it awesome, as expected for a Nic Logue adventure. This scenario is able to creep people out, and it's inspired at least one player to have his character quail in dread whenever the museum is mentioned again (after which he'll always explain that the negative reaction is in character only with "I am loving it"). The mists and their effects are also awesome, but with a warning of a potential for anti-awesome if you have an Int or Cha caster whose player cares more about effectiveness than the flavor.

I really liked the potential of the first encounter. Unfortunately my party all made their saves. I also liked the two encounters in the smaller exhibit rooms (one with a variety of undead, another is a fake out). The scenario mission and faction missions do a good job of making sure the party explores the whole museum, even though they could walk straight to the BBEG. The atmosphere of the museum can be played up to make this a pretty decent spooky-suspense style module. My biggest complaint with this module is that at 1-2, it was a cakewalk for my party. I don't think they felt threatened even once. The final encounter was particularly anticlimatic (they finished it it two rounds with ease). The consensus seems to be that this is a really fast scenario, but my players took 5 hours to finish.