High school earth science teacher here, and I just want to add my two cents to this fascinating thread.

There was a really good episode of NOVA a few years back all about this very subject. I'm sure anyone could find it on the PBS NOVA site, or You tube. If I recall the details correctly, they said in the event of a geomagnetic pole reversal, the earth's magnetic field would weaken, and then around six or so mini north and south magnetic "poles" would take the place of the regular north and south magnetic poles as they exist today. Then the flip would occur after that, with the normal north-south configuration reforming, only in the reverse orientation.

This re-orientation could happen over the course of only a few decades, if I recall correctly.

I think there wouldn't be much of an increase in harmful radiation as a result of the weakening of the earth's magnetic field because the earth's atmosphere does such a great job of shielding the surface from ionizing radiation. Remember that the geomagnetic field shifts and concentrates the incoming charged subatomic particles from the CME towards each of the polar regions, where they interact with the upper atmosphere, ionizing the atmospheric gasses, and causing them to flouress, resulting in the auroras. Most of the energy from the radiation is absorbed by the upper atmosphere and re-radiated as visible light. Inuit and Siberian people don't (as far as I know) suffer from increased cancer rates, even though they live under the northern lights all through the dark of winter months of every year.

Don't confuse the auroras with the ozone "holes" in the polar regions. Cancer rates might be increased in polar regions as the result of increased ultraviolate light as a component of sunlight during the summer, but not from the types of ionizing radiation that we're talking about from coronal mass ejections that cause auroras.

The scientists who were interviewed for the NOVA episode didn't seem to be too worried about negative economic impacts. They said our present-day electrical grid would be vulnerable to the kind of blackout that happened in Montreal, but we could adapt with enough advanced notice. Satellites would be vulnerable as well, but future satellites could be hardened against any increase in radiation that might occur in space.

They seemed to be more excited about the prospect of having the stunning auroras all over the globe every night, than fearful of any possibly negative consequences from it.