Let me start by saying I don't like the idea of a whole city of Supermen flying around. It negates Superman's coolness, and by having him basically follow Alura and the rest of the Kryptonian leadership around, he's been reduced to a guy who seems to do nothing except say "Yeah, but!" and "You can't do that!" all the time. The story in this collection is powered by Alura Zor El and General Lane, Superman is basically a tag along.
There are some great moments, but even these don't deliver quite as well as they could. I love the idea of the Kryptonians taking out Supes' rogues gallery and banishing them to the Phantom Zone. Having human cops die while guarding those cons is a great move too, as is bringing in the JSA and JLA to confront the Kryptonians about what they've done. When things break down (as they had to) I loved seeing Hawkman, Mr. Terrific, and the others try to hold their own against thousands of Supermen. But if you are doing something like that, make it BIG. Bring in EVERYONE. Where was Shadowpact? Where was the rest of the JLA and JSA? This could practically support a mini-series, so the encounter felt a tad rushed to me.
The cameos in this are pretty fun, although I vastly prefer Tim Truman's Creature Commandos to the ones Geoff Johns re-introduces here. And hoo boy, I'm mad that James Robinson remembered Agent Liberty. I knew when he first showed up that he fit the bill for one of Robinson's dramatic kills, and I was right. Liberty spends the whole trade crawling around some vents. He's immediately killed the moment he gets out. I know he's not a classic character or anything, but why not just make up some new cannon fodder?
I do like the development of New Krypton as its own planet, so I'll get the next trade from the library too, but man, I really need Superman to take a more active hand in the proceedings.
I do like the Superman house style these days. Pete Woods, Renato Guedes and Jamal Igle have a great balance between Silver Age design and modern realism.