Regarding the universe, note that the wiki points out that it's contradictory info. There's three different things that are supposed to be occuring in that setting that can't possibly be occuring in the same setting. I'd just ignore the tidbit about the universe, as it's not really relevant to the show.
Also, they're not so much using Aqualad from Brightest Day, as Geoff Johns liked his design so much that he pulled him into mainstream continuity, writing his origin story into Brightest Day. Of course, it's a different origin story, they have different names, and really the only thing they share are being black and having those water swords (and supposedly his being Black Manta's son, though cartoon hasn't confirmed that yet).
As for the show itself, it honestly bugs me for the most part, partly because I tend to have a strong distaste for "Darker and Edgier" treatments, and Young Justice was one of my favorite comic books due to it's lighthearted and humorous approach to teenage heroes.
So I feel the treatment is kind of a travesty, and feels more reminescent of the Titans series that followed it (which actually, I also tend to not think fondly of) after it was cancelled. And really, I wish they'd just called it Titans, and separated it from the Teen Titans cartoon that way (there's how many batman shows of different flavors without issues there?), than call it Young Justice when it has -absolutely nothing- to do with the comic book of the same name.
The creation of a new Aqualad also bugs me, as I don't see why they had to create this Marty Stu piece of shit character. He was created entirely to serve as the ethnic token character, but so that it's not so obvious that's his role, oh look, he's also made the LEADER of the group. And his personality SCREAMS "I'm a Marty Stu! Love me!".
Keep in mind that the comics had some time ago introduced a perfectly ethnic -and- female version, Aquagirl, who was a hispanic character and already existing. They couldn't have used her in the show for some reason? Did they need to keep a testosterone quotient that was higher to the number of girls?
And as nick mentioned, Miss Martian is a disturbing choice addition not just because she's younger than Martian Manhunter, but she's Jonzz's -niece- now (instead of a white martian), so either their race dies with 'em, or...
Arrowette being fused with Artemis...I can't really complain over the treatment, since she hasn't had an onscreen appearance. But that the costume in the promo poster is disgustingly green, and looks awful on her.
I don't generally have a problem with changes to Robin/Kid-Flash/Superboy, the reasoning for those changes make sense for the most part.
That said, it's also annoying that the show is using the 'teenagers are walking emotional time bombs' treatment to create GOLLY-GOSH-DRAMA. Well, except for Aqualad, because he's oh so mature and awesome, and look at his abs, I could just squee like a fangirl! *gags*
For all that though, the animation and fights were pretty damn solid and impressive. If you can go into the show without the mindset that this is supposed to be an adaptation of YJ, and don't mind emo/angry teenagers and think "darker and edgier" is awesome, this could be the show for you!
