Continuing in the weekly drops until Wine 1.6
is officially baked, Wine 1.6-rc3 was released this afternoon and has more bug-fixes.
Since going into the release candidate phase two weeks ago, no new features are being introduced into the Wine trunk code-base but only bug-fixes under this code freeze. As such, Wine 1.6-rc3 isn't too exciting unless you were impacted by one of the 30 bugs officially fixed in this release. If you're interested in seeing the list of bugs-fixed, visit WineHQ.org
In terms of the features added to Wine 1.6 over Wine 1.4, read the aptly named Features For The Upcoming Wine 1.6 Release