I leave my MacBook Pro at the office these days, and keep it plugged in most of the time. However, some folks have asked about battery life, so I figured I'd test it out today. I unplugged it when I got in and waited for it to sleep. 2 hours and 23 minutes. This is on par with my old PowerBook, but it's quite different from what MacRumors says (3hr 17min). I have a keyboard, mouse and 20" cinema display hooked up to it, but the display has its own power, so I doubt that effects the results.