If you don't know anything about the DC universe, and you're not in it for the Superman story, then well, this episode isn't for you. But that's not why this epsiode was bad though, I enjoyed the story, just everything else fell short in so many aspects.
This episode contained some of the worst acting I've seen in a while, and who the heck is writing these scripts? At times, I couldn't believe that someone actually said what they said. We've got a lot of references to Superman which was just about the only good thing about this epsiode with the Justice League hinting.
But other than that, this episode could have done way better in dealing with the Justice Society of America. The writing was weak, the acting was atrocious and it just wasn't up to Smallville's usual standard. This episode got way too much hype and it's definitely one of the most overrated episodes to this date.
Just watch this episode, then watch "Justice" from season 6. In quality, this pales to the season 6 episode. I just want my 2 hours back, this "episode" which might as well have been a feature film was nothing special.