I'm also getting substantially less time than ubuntu or XP, maybe not a full hour but definitely noticeable.
its not helped by not being able to turn bluetooth off (at least for me the option is greyed out)
but for me having OSX is worth it. At least better than XP. Ubuntu isn't an option for me right now as I can't get the 3G to work even with wvdial methods and many hours of CLI work (it dials but never manages to connect properly).
re sound issue, i had it too, and the above poster is right - reinstall dellefi and make sure u delete the old file