I always put it into the category of comic stories that want to be SO important (And... There's some good stuff in there. Some really great observations and commentary on Superman) and different but in the end winds up amounting to something that doesn't satisfy as a super hero story and doesn't satisfy as a genre story with pretensions of high art. It's just vague and ultimately empty. Azzarello's a fantastic writer but he dropped the ball badly with that story since frankly from the first chapter you never really understood what was going on or the players involved. There's some truly fantastic Superman moments in the story. The confrontation with the Elemental giants is a particular favorite of mine. But it doesn't hold together as a full story and once you do piece it together it's generally underwhelming. I put it in the same category as FINAL CRISIS or Morrision's other mind **** SEVEN SOLDIERS, which... apparently to really get FINAL CRISIS you had to have read all of SEVEN SOLDIERS which... Sorry Grant. A universe wide defining event series at the end of the day should have at it's core a story that a fan, especially a long time fan can easily follow.... But I digress.
Love Lee's art in FOR TOMORROW. Maybe some of his best mainstream work but overall the series swings and misses hard for me.