5YL was way ahead of its time. The SW6 concept was one of the best things ever, and we had both titles. That, IMO, was what they should have followed. Zero Hour basically was a new coat of paint on the Legionnaires, and Giffen's Legion got axed.
Honestly, that's one of the best runs of any comic ever. Anything could happen. They were young adults in a dangerous broken world, long gone from being wide-eyed kids.
It was a huge mistake not having Legion relaunched along with the rest of the DCU, but I think editorially did it more as a favor to Levitz's than anything. You can't believe how many people picked it up and were completely lost or disappointed.
I'd kill to have Brandon (Prophet) Graham on Legion, but he's sworn to never work corporate.