I like the Superman Animated Series, although its not as good as Batman: TAS or JL/JLU. I really liked Lobo in the series, he was great. I HATE Metallo in the series. He was ok the first time, but after his first appearance I can't stand to watch any more of the episodes with him (not counting his appearance in JLU or metallo in Superman/Batman - Public Enemies). The way the charactyer is portrayed just gets on my nerves, and I didn't really like the character in the first place. so, of course, he has to appear in a bunch of episodes. Personally, I think he's a lamer villain than Toyman, and Superman:TAS actually got Toyman right.
I just rewatched World's Finest today. Its a great 3 parter. I liked Harley fighting Mercy several times throughout the episode. My only problem with it is the stupid looking Joker design, if he had his original B:TAS design, this story would be pretty much perfect. I'm glad the people in charge figured out that the Superman:TAS style design of Joker was stupid/unpopular and switched back to classic Joker for his JL appearance.