@Boosterrific- I haven't read any of Robinson's JLA, so I really can't judge, but I think you're right. JLA is an army/gathering of heroes (fast, standalone stories) and JSA is more of a family dynamic (slower paced, character driven stories), I guess that's one of the reasons I prefer JSA. That's not to say I like slow for SLOW's sake, see latest JLI for examples. Also, I expect fans of Morrison's JLA are probably not fans of Robinson's, two VERY different writing styles.
@Morgenstern- While I haven't read Earth-2 yet, I understand from Robinson that the modern setting is just to give readers a familiar world setting. I don't know if there even is a JLA on Earth-2, the early stories with SM, BM, and WW (the Trinity) seems to be just to establish their existence in this world. Historically SM and BM do predate the JSA, with WW first appearing a short time later. This series seems be a kind of WHAT IF the members of the first super-team (JSA) were young and just starting out in the modern world. For "midlife crisis" me, it's nice to see DC's old guard heroes in their prime again, and taking on new challenges for the first time. Younger readers might have a harder time relating, but I hope the book succeeds, on it's own AND for it's (alternate universe) nostalgia value.
Honesty guys, if FLASHPOINT hadn't been such a hack, I probably could have accepted this kind of "clean slate" reboot for the New 52 Earth-1(?) "core universe" books. Meanwhile, if you're (at all) interested in Robinson's "early" JSA work, I recommend "THE GOLDEN AGE", a JSA Elseworlds story that takes place in the post WWII "McCarthy" era, and could just as easily be an "in continuity" UNTOLD TALE of the original team. And the villain is... **SPOILER**, nope not gonna spoil it. It's like a mini-Watchmen, and confidentially, the direction/flavor I'm hoping he gives the new EARTH-2 series
Short James Robinson Interview on Earth-2http://kotaku.com/5906695/earth-2-lets-james-robinson-re+invent-dc-comics-biggest-superheroes