The Norwegians have released Opera 12.10 this morning. While Windows and Mac OS X improvements are the primary focus of improvements for this release, an updated Linux version is also available.
Opera 12.10 brings various improvements to Windows 7/8 and then on the OS X side it has proper support for OS X 10.8 Mountain Lion functionality, including support for the retina displays. The only other major feature advertised that is platform agnostic is support for a wide array of new extensions.
Among the extensions highlighted for the new Opera 12.10 release are for Twitter, Facebook, Pinterest, StumbleUpon, and TED.
More details can be found from Opera.com or from the Opera 12.10 video embedded below, which is highlighting the new Opera web-browser extensions.