The first release candidate for X Server 1.9 was delayed because of the Intel Linux graphics driver (xf86-video-intel) not building against the latest 1.9 code due to a driver issue, which is now fixed-up so Keith Packard went ahead and created this first release candidate: xorg-server 188.8.131.521.
There isn't anything too incredible to be found in X.Org Server 1.9 for end-users, but there is the RandR 1.4 support with per-CRTC pixmap support. As was said in that last status update, "This support, as described in the Resize and Rotate extension documentation, provides "multiple scan-out buffers which applications can create and assign to arbitrary collections of crtcs. These pixmaps can be associated with a window for use with OpenGL or drawn to directly." A RRSetCrtcConfigs request has also been added to the RandR 1.4 specification. Intel has a branch of their xf86-video-intel driver with RandR 1.4 support while the other open-source drivers are likely to follow soon."
There's also bug fixes and a variety of other work that's been collected since the X.Org Server 1.8 release earlier this year. Expect a few more release candidates to come before the August 1.9 release.
The 1.9 RC1 release announcement can be found on xorg-announce.