Besides taking advantage of raw mouse events on X Input 2, which should hopefully address the problems of the mouse input being re-directed in some windows/full-screen games, there is also support for mouse pointer clipping. Outside of mouse/input fun, there's also the first steps of a DIB engine implementation, many properties supported in DXDiag, a new security tab in the Internet control panel, and improved video playback under Mac OS X. There's also the usual bug-fixes.
As mentioned in the Wine 1.3.18 release announcement with the appended change-log, there are also various Direct3D changes to be found in Wine 1.3.18. However, none of the D3D changes jump out as being too prominent.