In a nutshell, The RetConQuest is a solid adventure that seems -- structurally -- more appropriate as an introductory adventure rather than as a stand-alone adventure in an ongoing campaign.
The core conceit of 'normal humans' remembering their superpowered selves and slowly/instantaneously regaining their identities and abilities in an alternate timeline is a good one, allowing new players (and characters) to slowly be introduced to the character creation and task resolution rules of Icons without necessarily abandoning the game narrative completely. The plot twists seeded in the "initial" and "final" confrontations with Tempus Khan are also useful in terms of helping fine tune characters created in the course of play, in addition to being a clever, limited-novelty nod to the nature of battling time-conquering villains.
For an ongoing campaign, however, I have a preference for more scenes and encounters that would allow the GM to present a series of encounters with heroes, villains, and normals from the regular campaign and how their lives are different from what is remembered. There was only one opportunity for this in the published adventure, though a clever GM could arguably extend or spread out such scenes.
Finally, there were a small number of typos that could have been fixed (and still can be through the magic of updated PDFs): like the "page @@" incident and a missing apostrophe.
All in all, a solid, clever adventure and a potentially great beginning for a great campaign!
[4 of 5 Stars!]