I'm not sure the people who make the JLU animated series fully understand the concept of television seasons. Season 1 of JLU (which was also sorta season 3 of the Justice League series) ended yesterday, with the second half of a fairly strong time travel episode. Season 2 starts… next Saturday. In a series where one often has to wait a several weeks between episodes, airing the season opener one week after last season's finale is a bit… odd.
Still, scheduling issues aside, JLU is an excellent show. It is truly all-ages in its appeal, and episodes are written by some of the finest writers in the genre (a recent episode was penned by Warren Ellis, and next season promises an episode by Gail Simone). The conceptual change between JL and JLU, which allows the writers to use any hero (and, obviously, villain) in the DCU, makes for an interesting variety of stories.
The season finale was a bit odd in the fact that it only featured Green Lantern, Batman, and Wonder Woman. But is was a decent story, with interesting reveals regarding the future of the animated version of the DCU.