The final show is interesting for how little screen time the original Justice Leaguers--Superman, Batman, Wonder Woman, Green Lantern, Flash, Martian Manhunter and Hawkgirl--feature in. Of those characters, probably Flash and Green Lantern figure most. When the show became "Unlimited" they added just about every character from the DC Comics universe. So you get to find out a lot more about characters like Vigilante, Huntress and my new favorite, Question.
I'd really like to know more about Question. Check out the action figure:
Crusading journalist Vic Sage made a name for himself by opposing the forces of crime. But when reporting on criminal activity proved to be ineffective, Sage adopted the identity of The Question, a faceless (thanks to the blank mask he wore) opponent of injustice! The action figure features multiple points of articulation, stands approximately 6.375" tall and comes with a removable hat that has his mask attached.
There are also a ton of "supervillains"--in watching one of the features, I learned that the comic heads who wrote the show were digging through old books to find old characters. Often they decided to put on characters who would otherwise "never be animated". The whole thing gets a bit unwieldy, but it is a lot of fun. In this final season, there is a series long arc even though there aren't two-part episodes like in earlier seasons. It's not quite as interesting as the season 1 Justice League Unlimited arc involving a government conspiracy to keep the power of the Justice League in check, but if you've seen the earlier shows it's pretty good.