Marco Tabini wrote an article for Macworld about why battery life is such a big deal to Apple. I couldn't agree more. Across the product line, Apple wants to be able to put those cute little green clock animations in their presentations. Apple aims at the fat 90% of the market and while a few points better on a benchmark are nice, what they really want is for one non-geek to tell another non-geek about how he flew from Honolulu to Boston without having to plug in.
On that theme, I'd always thought the idea of an ARM-based (or some other based of an ultra low power chipped) Mac as something years and years into the future. After seeing Apple unveil the 64 bit A7 for the new iPhone 5s, I'm not so sure anymore. I know a lot of people that would be interested in a Mac (even a bit underpowered) that ran for 20 hours.