Throughout the first five issues, we've seen the different characters come together. This hasn't been the typical Justice League story. There's been fighting between members as well as characters getting thoroughly defeated. Jim Lee has given us plenty of big epic battle scenes while Geoff Johns has subtly laying out the groundwork of what the team (and DC Universe) will become. Many have asked what happens to change the atmosphere between this story taking place five years ago and the present. A lot of that is answered here.
I've applauded Johns' gathering of heroes in this arc. The heroes are not used to working with others and they've never faced a threat of this magnitude. In order to save the day, they can't and won't simply hold hands and defeat Darkseid together. Each plays a different role in the battle. Each character has their own strengths. It's up to them to use their abilities and figure out how to combine them in order to end the battle. As for Darkseid, wait until you see what his true intentions are. We get to find out what he's really after.
This issue also begins a little differently. It starts out with a narration from an outsider. We know the general populace isn't completely used to or comfortable with superheroes. They've never seen this level of destruction and witnessing the gathering of these powerful individuals is something to see.
One complaint I've heard about this series is the price and the amount of content inside. We know we're supposed to be getting back-up stories and we do get one in this issue. It wasn't announced before and you might have heard the information as it was leaked out but we get a heck of a back-up.