The gain from the mobile update daemon is rather small. However a nice thing i have recently discovered is that mounting a disc w/ 'noatime' as an option decreases disc spin ups because the disc is no longer written to on every file access. Who uses atime on a laptop anyway.
Besides, replaces in updated in debian will be a serious pain. And the gain is maybe 2 - 5 minutes. Not worth it when there are bigger fish to fry.
