"Pack it to the max" would be a good summary of the iPhone efficient interface. But it could be better according to Edward Tufte. Watch the iPhone interface explained in this video.
"The iPhone platform elegantly solves the design problem of small screens by greatly intensifying the information resolution of each displayed page. Small screens, as on traditional cell phones, show very little information per screen, which in turn leads to deep hierarchies of stacked-up thin information--too often leaving users with "Where am I?" puzzles. Better to have users looking over material adjacent in space rather than stacked in time."
"The iPhone platform elegantly solves the design problem of small screens by greatly intensifying the information resolution of each displayed page. Small screens, as on traditional cell phones, show very little information per screen, which in turn leads to deep hierarchies of stacked-up thin information--too often leaving users with "Where am I?" puzzles. Better to have users looking over material adjacent in space rather than stacked in time."