Just randomly grab a online review:
Part of the draw of Intel's fourth-generation Core processors is that they
are supposed to provide a significant improvement in battery life. On our
LAPTOP Battery test, which includes continuous Web surfing with the display
brightness set to 40 percent, the VAIO Pro 11 ran for 6 hours and 23 minutes
before calling it quits. The average ultraportable notebook lasts 5:55.
hopefully there will be a real head-to-head benchmark between top Ultra
books and MBA. The tradeoff is clear, better screen likely will lead to
worse battery life.