I had mused in an earlier post that we, as a society, were lucky that the magnetic field was around when navigators really needed it (the past several hundred years) and that without it, a global civilization might never have developed. Turns out I understated the other benefits of the magnetic field:
Many aspects of life today would be literally turned upside down, both for humans, given our dependence on magnets for navigation, and for migrating animals which use an inner compass.
We would also be more exposed to deadly busts of solar radiation, from which we are normally protected by Earth's magnetic field. And the loss of that shield would cause solar particles to smash into the upper atmosphere, warming it and potentially causing wrenching climate change.
I'd chance the loss of the magnetic field now in terms of navigation -- global commerce can safely make the transition to GPS with only minor disruption if the magnetic field slowly vanished. Also, the migratory animals might get confused but would probably bounce back in some form. But the wrenching climate change could ruin your whole day.