XFree86 3.9.15 is a ``work in progress'' snapshot of the XFree86 4.0 development code. It is the first in a series of snapshot releases leading up the the 4.0 release. The plan is to release a new snapshot every four to six weeks. The target audience for this release is developers and others who are comfortable on the bleeding edge. This release is not targeted at beginners. Also, most end users will find life easier using our latest 3.3.x release. While we welcome bug reports and feedback about this release, we don't have the resources to provide user-level support for it. If you're not comfortable dealing with those sorts of things yourself, then the snapshot releases are probably not for you.
This code is very much work in progress. Many of the interfaces may change without notice between now and the 4.0 release. The driver design has changed significantly compared with the 3.3.x versions, and only a small number of drivers have been converted so far. That means that this release does not support a wide range of video hardware. Some of the drivers and new features are well developed and reasonably stable, while others are not.
Information on this release's features and their status can be found in the Release Notes.