The main story of "What Lorna Saw" had nothing to do with the Apocalypse story, but the ending regarding Lorna, and then several side stories tied in... such as with Gazer and Pulse's inclusion in the team, which led to his semi-important role in the conclusion of the Apocalypse storyline.
And I thing I was most interested in the idea of the story. The only dialogue that really got to me was Apocalypse himself and his self doubt. I felt that Milligan had a lot of great ideas in the story, but he did fail on some execution... such as I believe that his reasonings and leading up to of Gambit becoming a horseman was belieable... however, he didn't pen it to paper well enough to make it fly.
And as for it not amounting to anything. There were definately some lingering storylines from that arc that's played out or will be played out...
1) Gambit and Sunfire are under Sinister, and that will play out in the upcoming "Mutant Messiah" crossover event.
2) Polaris was given her powers back (or a varient of it) and she's had them ever since.
Yeah, that's about it I guess.
One thing I did like that nothing came of, however, was the character "Pulse." I didn't like him at first, but thought he came into his own during that arc. When we realized that though he was really into Rogue, but not like Mystique was wanting, and that he was a thief with a cool power, but was a little bit of a coward (which could be neat if used well) I was sold on him. I was excited to see what would come of him and if he'd actually join the team. Sadly, after that arc he vanished to be never mentioned again. I like Carey, but it sucks that he just went and ditched the character and didn't even give a reason. I hate when they do that.