DC has begun their "The New 52" relaunch with Justice League #1 by Geoff Johns, Jim Lee and Scott Williams. I think it was a good opening to their initiative. Read on for specifics!
Probably the one thing that I appreciate the most about Johns' take on the formation of the Justice League is that he is injecting a good deal of humor into the comic. It is a nice to see that established right off the bat in the new DCU. Combining that with a fast-paced and yet characterization-rich story was a smart move, since if you have Jim Lee drawing your comic book, you really need to put a lot of cool action into the story (as that is what Jim Lee does best), but you don't want your first issue to be devoid of characterization, and Johns struck an impressive balance between the two.
The clearest critique of the issue would be that for the first issue of your relaunch and on a book titled "Justice League," it might have been better to have the Justice League in the actual comic and not just have it be the first meeting of Batman and Green Lantern (with set-up of Cyborg and Superman). I think that is definitely a fair criticism, but at the same time, I really don't know if "I would have done this differently" is necessarily that compelling of a critique when what Johns actually did do worked fine. And it really did work well as Johns did strong character work with both Batman and Green Lantern. Honestly, it reminds me a bit of what Frank Miller did with the two characters in All Star Batman and Robin, particularly the whole underestimation of Batman angle (which Johns played for laughs very well, "You're not just some guy in a bat costume are you? ARE YOU FREAKING KIDDING ME?") while Batman considers Hal to basically be an amateur who just happens to have a powerful weapon.
Tying Cyborg's origin into the Justice League's formation is a smart decision, as Johns really needs to play up why Cyborg is a part of this particular League, and making it be part of him becoming a cyborg makes sense. I also like the way that Johns holds basically true to Cyborg's original origins while fitting it into the current structural narrative (that this is a time in the DC Universe where there ARE no "superheroes," just superpowered beings).
The whole "this is where superheroes start" idea looks like it will be played up heavily in the second issue, with the confrontation between Green Lantern, Batman and Superman. That initial high level of distrust makes sense, and it is something that John Byrne played to good effect in Man of Steel.
Making Darkseid be the initial bad guy for the League (and maybe not even THE bad guy, maybe just his minions, making Darkseid an even bigger foe for a later date) is a great idea. The notion of tying your biggest villain in with the creation of your biggest superhero team makes a ton of sense. I particularly enjoyed the reveal that Darkseid's existence was unknown to the Guardians of the Universe. I love the attempt to make the Fourth World seem more detached, like they really ARE "New Gods" and not just "alien race #143040."
All in all, this was an enjoyable issue, with crisp action and good humor and some of Jim Lee and Scott Williams' best art work on a comic since Hush! A good start to the new DCU!