The full extent of the update is still unknown, but as is usually the case, you can use Google Maps to determine for sure whether or not a specific area is fresh. This new imagery isn't in Google Maps yet, so you can compare Earth vs. Maps to see what's new; the fresh imagery is already in Google Earth, but the old imagery is still in Google Maps. If you compare the two side-by-side and they're not identical, that means that you've found a freshly updated area in Google Earth!
[UPDATED -- 24-February, 4:16pm EST]
- Australia: Melbourne -- thanks 'David'
- Bosnia Herzegovina: Various areas -- thanks 'Andreas'
- Croatia: Various Areas -- thanks 'Andreas'
- Germany: Hohenfels, Marl -- thanks 'Andreas'
- Norway: Various areas -- thanks 'Andreas'
- Romania:Various areas -- thanks 'Andreas'
- Sweden: Areas along the western part of the country -- thanks 'John'
- UK: London -- thanks 'Carl'
- United States: Illinois (west central) and Tennessee (southern sections) -- thanks 'KennyB' and 'Wes'