Here's the official changes worth mentioning:
- New sound driver architecture for MMDevAPI.
- Better support for relative mouse events in DInput.
- Debugger support for the ARM platform.
- Various improvements in D3DX9.
- More MSVC runtime functions.
- Various bug fixes.
The complete list of bug-fixes plus other information can be found at WineHQ.org. The improved Direct3D 9 / DirectX 9 support comes from implementing a whole lot more functions for the Microsoft API.