Having now read through the book and digested its contents, I'm posting about the various settings that the book features. One of the points of the adventure is to showcase these settings, so I'm going to comment and grade them on how well they did so, and make suggestions on how to better get the overall "feel" of the settings when that is lacking.
Chapter 2: The Wizards Three
The first part of the Rod of Seven Parts is hidden in an isolated and secret meeting place for agents of Lolth known as Web's Edge, deep within the Underdark of the Sword Coast area of the Forgotten Realms.
Setting featured: Forgotten Realms/Underdark
Showcase Grade: 1/10
How they showcased the setting: With very little, actually. The location isn't very evocative of either the Forgotten Realms or even the Underdark. It could just as well be placed in any world where Lolth has worshipers, and there's no way of knowing without being outright told that it's located in the Underdark instead of, say, some small cave immediately accessible to the surface. The spider-dragon is at least reasonably cool, though.
How to showcase the setting better: Have the portal open some distance away from complex, so that the adventurers have to travel at least a bit through some Underdark locations to get there. Have them visit fungus-filled caves (perhaps one with a myconid settlement), meet a duergar or deep gnome trading caravan, or undergo a drow ambush. Anything beyond just appearing next to the door to the complex! Perhaps Alustriel's portal takes the party to her home city of Silverymoon, and the group has to make a bit of a longer, but more immersive, journey from there (I'll be suggesting such longer journeys for several chapters).
Chapter 3: The Lambent Zenith's Last Voyage
The second part of the Rod of Seven Parts is to be found within the body of the dead god Havock on the Astral Plane.
Setting Featured: Spelljammer
Showcase Grade: 8/10
How they showcased the setting: There's a Spelljamming ship, and it takes place on the body of a dead god. There are githyanki NPCs and another NPC disguised as a giff. All pretty Spelljammer-y!
How to showcase the setting better: A few more Spelljammer-specific creatures would have been nice. The main thing, however, is that the ship has crashed, so no fun sailing through the Astral. The party could definitely start some distance away and need to hitchhike or otherwise hire an actual functioning Spelljammer ship to get to where they need to go (although said ship would likely drop them off some distance away so as not to suffer the fate of the Lambet Zenith!), resulting in some swashbuckling attempted boardings and monster attacks. They could even start at the Rock of Bral and hire a ship there to really get a full, flavorful experience in the setting.
Chapter 4: The Ruined Colossus
The third part of the Rod of Seven Parts is located in the ruins of a huge warforged colossus in the Mournland of Eberron.
Setting Featured: Eberron
Showcase Grade: 10/10
How they showcased the setting: Exceptionally well. The Mournland is depicted very faithfully, and there are warforged featured prominently. The fact that portal is some distance away from the part of the rod the party is searching for means there is plenty of time for them to experience some of the setting's unique features. It's all very well done - someone very familiar with the setting must have been assigned this part.
How to showcase the setting better: It's really just quibbles, but they could have featured more Eberron-specific monsters (living spells come to mind). If you really wanted to go all-out, have the portal take them to a friend of one of the Wizards Three in Sharn, and then they can take a lightning rail to the edge of the Mournland. Throw in a couple of Sharn-specific and rail-specific encounters/adventures, and you've got a pretty decent taste of what Eberron can offer!
(As it's getting late and this post is getting long, I'll continue with the remaining settings in my next post)