We're excited to announce that the second Flex 4 SDK beta 2 is now available for download! Check out the Labs page and the Flex 4 Open Source page for more details. Also, be sure to check out Matt Chotin's updated What's new in the Flex 4 Beta and Joan Lafferty's Differences between Flex 3 and Flex 4 articles. This beta release also coincides with the beta 2 releases of both Flash Builder and Flash Catalyst.
We received great feedback on beta 1, which we incorporated into beta 2. We hope you'll keep the discussion going on the Labs forums.
Enjoy!
Looking forward to giving this a try.