Starting with Solaris Express Community Edition Build 107 there is X Server 1.5.3 and Mesa 7.2. The updated X Server brings numerous improvements and the updated version of Mesa allows for improved open-source 3D graphics. All of the other X.Org 7.4 drivers and components have also been updated in this latest OpenSolaris build.
While their OpenSolaris X stack is up-to-date, X Server 1.6 and Mesa 7.4 are on the heels of being released. Let's hope that it doesn't take as long to get these new packages into OpenSolaris.
The SXCE Build 107 release announcement can be found on the OpenSolaris Forums. The list of X.Org changes can be found here and specifically this bug entry.