Now that the new stable is available for download, I would imagine that a new release build isn’t too far off…
You can download the latest version of the SDK here: http://opensource.adobe.com/wiki/display/flexsdk/Download+Flex+3
From what I can tell, it mostly comprises of bug fixes – no fancy new functionality seems to have been added. But I guess you will have to find out for yourself by trawling through the nightly release notes (joy :S)… If you find anything noteworthy, let me know, I only noticed a few changes in some of the utility classes.