It's arriving about two months later than originally scheduled (and didn't arrive in 2008 like Intel wanted), but X Server 1.6 has been officially released this afternoon and it wasn't 212 days late like the infamous X Server 1.4.1 release.
X Server 1.6 introduces the server bits for Direct Rendering Infrastructure 2 (the 3D bits can already be found in Mesa and the Intel driver), X Input 1.5 with device properties, Predictable Pointer Acceleration, and RandR 1.3. Beyond those key features, there are also a number of bug-fixes, EXA improvements, and various other improvements.
What this release doesn't have, however, is X Input 2 or Multi-Pointer X even though MPX had entered the master X Server tree nearly a year ago. A draft of the X Input 2.0 protocol specification is available. These input features are being held off until X Server 1.7 with X.Org 7.5.
While there are some EXA improvements within X Server 1.6, this release doesn't have support for the UXA acceleration architecture. This Intel-spawned 2D acceleration architecture based upon EXA is still living within the xf86-video-intel driver and hasn't worked its way into the X Server. Originally it was expected that the UXA changes would work their way back into EXA, but during FOSDEM this year we learned it will not be merged into EXA. The UXA API is the same as EXA, but internally it depends upon the Graphics Execution Manager for its memory management needs.
Version 1.3 of the Resize and Rotate extension in X Server 1.6 supports projective transformations, panning, and other new options. More details on that can be found in our RandR 1.3 Explained, Demonstrated article along with a video showing some of the RandR 1.3 features. DRI2, of course, allows a number of new features such as the ability to enable direct rendering to redirected windows.
While X Server 1.6 is being pushed as a standalone update without a new version of X.Org officially arriving, several other X.Org packages have been updated recently as well. Earlier this week Intel had pushed out a big bug-fix update, the xf86-video-ati driver reached version 6.11, and even the Voodoo Linux driver was updated. There has been talk that X.Org 7.5 could be released in April, but the chances of that taking place are extremely unlikely. It's our prediction that it will be at least July or August before X.Org 7.5 / X Server 1.7 is released, but more than likely it will be out in September.
For those not interested in building all of the latest X.Org packages from source, most distributions should adopt these packages in their Q2'09 updates. The proprietary NVIDIA driver is compatible with X Server 1.6, while the proprietary Catalyst driver from AMD doesn't yet offer any support for this updated X Server.