Are you talking about the SDK or the IDE?
The SDK is perfectly safe to start using for production projects already, from svn trunk (in my opinion)
If you are talking about the IDE, then a free version for developers would, i think, leave adobe with VERY few people let to actually buying it
tinylion development & design
I'm talking about the IDE. The reason I asked about the "free" version is because ColdFusionBuilder 1 has a 3 connection limited, free version for developers. But ya, everyone using FB4 would be a developer. Dum question I supose.
I'd just follow the official Adobe Flex blog at http://blogs.adobe.com/flex/ and I'm sure that page will be updated in "early 2010" when Gumbo is released (source http://opensource.adobe.com/wiki/display/flexsdk/Gumbo). You can also join the Adobe Flex facebook group at http://www.facebook.com/adobeflex.