There have been many many improvements and plenty of new features added. Listing just a few (doing no justice to the complete change set)
— Many new toolbar icons.
— Support for alpha blending in image lists.
— Much more complete shader assembler.
— Support for Arabic font shaping and joining.
— A number of fixes for video rendering.
— Font anti-aliasing configuration through fontconfig.
— Improved handling of desktop link files.
Win64 support is the milestone that marks this release.
Please test your favorite applications for problems and regressions and let the Wine team know so fixes can be made before the final release. Find the release candidate here.