Don't be fooled. The 1990 map was an oddball, captured during a cold run of years.

1960 Map

2006 Map

The map being promoted by the Arbor Day Foundation is the one prepared by the American Horticulture Society under a grant from the USDA in 2003.
It was not accepted by the USDA, which found it contained numerous errors.
The current USDA map, approved in 1990, is based on recorded temperatures during the period from 1974-1986, and remains the official Hardiness Zone map of the USDA.
All of the modern day record low temperatures in the Atlanta area were established during the decades of the 1960's, 1970's & 1980's, with the lowest temperatures ever recorded here, occuring during 2 nights, January 21 & 22, 1985. -8°F (ATL). -10°F (PDK) & -12°F (Stone Mtn).
Those 3 decades have been referred to as the; "Mini-Ice Age", by old-timers (my circle)!
Gardeners, like myself, have been "pushing-the-envelope" regarding plant hardiness, every since we turned our 1st shovel-full of soil. Often successful, some times-not!
If you find plants rated hardy only to USDA Zone 8 or 9 and you want to try your luck, why not? There are microclimates in every garden and with some protection, they could be successful.
IMO, the Hardinesss Zone map produced by the AHS & ADF are just pretty colored maps, nothing more, nothing less.
Rb

'Does this scare anybody else??'

No, the ice storms up there scare me:)