Uhhh, if the flip is 180 degrees, why would compasses be a problem? I think I could adjust to the pointy end pointing south on my trusty field companion. (Although I'm sure compass manufacturers would make a fortune telling us we all had to buy new ones so the arrow still pointed north.)
The last Magnetic Field reversal happened during the 11th Century B.C....and the events were catastrophic...
It happened at the close of the Trojan War, and plunged the then civilized world into a 400 year "Dark Age".
It caused the very rapid melting of the Ice Age Icecaps...Egypt experienced extreme floding at that time, and the Sahara Desert became a combination Savannah-Swamp.
It initiated the massive flooding of Lake Titicaca on the Peru-Bolivia Frontier, and extinguished the City of Thiauanacho [sp] near the Lake, a city some contend dates to 17,000 B.C.
No, the shifting of the Magnetic Poles is not to be trifled with...on Earth.
It happens every 22.2 years on the Sun!