Originally Posted by dcg
Why do you say especially the 15" line? Primary benefit of Haswell is better integrated graphics; the 15" model has dedicated graphics. Battery life will get a bump as well, but that'll benefit all models (and the 15" already has better battery life than the 13" under light usage).
2 ways - either they can add in an underclocked graphics card to handle the performance needs (like they have been doing but this time without taking such a hit) and, again, reduce the battery strain, or they could eliminate the graphics card all together (which I don't see them doing quite yet) and just run it off the integrated chip.
Also, the Haswell architecture is supposed to improve battery life 30%. Whether we'll actually see that is a different story, but I think it'll definitely make the 15" a game changer if it can handle the needs of the retina screen AND hold out MBA-like battery life.