[According to their tests][link], the new 15″ MBP lasted almost TWICE as long as the previous model– a total of about 5.5 hours to a charge. That is a *huge* jump, and as far as I can see it is unprecedented. They say:
>There’s only a 46% increase in battery capacity, there shouldn’t be a ~100% increase in battery life…ever.
I figured Apple must’ve had a damn good reason for making the battery internal, and it looks like this is it.
[link]: http://anandtech.com/mac/showdoc.aspx?i=3580&p=4 “AnandTech: Apple’s 2009 MacBook Pro: Battery Life to Die For”