stock internal hard drives do not spin nearly fast enough to use for video editing with a power book...even if you are only using miniDV format video and capturing through firewire.
you will do nothing but drop frames.
you MIGHT be able to use the internal drive if you were talking about low res options like offline or less than full frame / rate video.
for DV i'd suggest at least 7,200 rpm drives and to get that for the time being you probably are looking at dragging a firewire drive with you...and more than likely one that ISN'T powered off the firewire bus.
those, my friend, are the breaks.
someone has mentioned IBM is coming out with a 7,200 rpm internal drive. If you can get one of those, you might have a shot. But in the mean time, the dream of the powerbook and a DV cam / final cut as all you need to edit video in airports and coffee shops is still kind of just that...a dream.
you're going to need a faster hard drive than what's tucked in that slick titanium package. that's ok. external drives are cheap these days.