I've read both issues of Earth 2 and just the first issue of World's Finest, and GI Combat.
Earth 2 has been really cool. It's interesting to see the alternate reality and see the Justice Society be the focal point. Although I'm not too keen on the Flash's costume. I was hoping for the old army hat with wings.
Also, issue 2 was the big reveal of Alan Scott being gay, and Mr. Teriffic being thrown into Earth 2.
As for World's Finest, I do like it, too. It's kind of the opposite or Earth 2 though, as it's people from Earth 2 somehow being stuck here on Earth 1 right? Or am I just confused?
And I normally don't like War books, but GI Combat was really good. I especially liked the artwork in the first half with the dinosaurs. It's weird enough to keep my attention.