Catalyst 12.3 isn't too interesting in terms of features or bug-fixes, and it doesn't have X.Org Server 1.12 support. However, Phoronix readers have already been quick to spot this driver's availability and have begun discussing it in the forums.
Most die-hard Linux enthusiasts relying upon the binary driver with ATI/AMD Radeon hardware are likely already using the early Catalyst 12.4 betas for Linux, which at least carries a few more changes over this month's official driver update.
The AMD Radeon HD 7950 under Linux is working fine with Catalyst 12.3 and I have more Linux OpenGL results from this GCN Southern Islands card to publish in the coming days.
For those on the NVIDIA side of the table that aren't using Nouveau, NVIDIA 295.33 was released last week for Linux as their latest and greatest driver with official support for the GeForce 600 Kepler series.
Go forth, as a Phoronix reader says about Catalyst 12.3, and "discuss, fight and insult each other" over this AMD Linux binary driver that's notorious and often controversial.