I have the Australian Country Variant of the 920 and I just installed and updated to "Lumia Black"; I have the developer preview of GDR3 and updated with no problems. My new firmware version is 3051.40000.1349.007. Unfortunately for the Telstra branded 920 owners, the Telstra 920 update is still showing "Waiting for approval" as well so it looks to be still in testing which matches that Telstra were estimating a February release for the 920 update in their latest updates thread from last year.
The Nokia AU support page for the 920 has been updated to include the updated firmware and features of Black / GDR3:
Nokia Lumia 920 - Software Update and Downloads - Nokia - Australia
The .Availability in Asia Pacific web page still displays Black for the 920 as "Coming Soon":
Availability in Asia Pacific - Nokia
The one strange thing I have noticed is that in my Settings > About screen on my 920 the Hardware revision number has changed from 1.0.0.0 to 6.5.0.2. Everything else seems to be working well so far although I only updated 10 minutes ago so I'll see how it goes over the next day or so.