I collected the story at the time because I hadn't followed a big event in a while so it was kind of fun to do.
However, I didn't think it was that great. First of all Imperiex, like Doomsday before him, isn't really a character. He's just a threat. He's stated to be the creation and destruction force of the universe, he's the Big Bang and Big Crunch basically. He has no malice, no personality. If they just treat the story like heroes battling a natural disaster it could work, which the better issues did.
Second it doesn't make that much sense storywise to say that he is naturally occurring force that is destined to end the universe now when we already know the future with the Legion and such. Obviously the natural order of things is for the universe to survive for another thousand years at least. The Quintessence even put Superman on trial for altering the fundamental nature of reality by stopping Imperiex. The Linear Men come to his defense, maybe because they know the universe is going to continue. Which is it?
The street level stuff offered the most memorable parts. The sight of Lexcorp tower burning like the World Trade Center. Supergirl trying to stop Topeka, Kansas from getting nuked (and failing). Pa Kent going missing.
They tried to beef up the body count so it was a Crisis-level event. Hippolyta had the most memorable death, perhaps. Maxima is killed off-panel, I think. But would anyone watching a current movie version know who they are? Guy Gardner was killed off only to return shortly after. The only success the heroes really had, as I recall, was the JSA saving Daxam from invasion. Would they spotlight the JSA?
I never quite understood giving Superman all the credit. As I recall the ending had Warworld absorbing all of Imperiex's destruction energy and Superman pushing it away through a wormhole. Pushing a planet is a nice show of strength but that's all really.
Also since Imperiex's energy was redirected back to the Big Bang giving us a double-Big Bang you would think it would alter the timeline just like Crisis and Zero Hour did when they reset the beginning of time, but there was no effect.
If they were to do what Marvel did with the Infinity War movie and take a few elements from the story and reimagine the rest, you might have the bones for a good movie. Thanos' plan in the movie doesn't really make that much sense either, but it didn't matter.
Superman becoming a Cosmic being at end to stop Imperiex prime was very cool!