This story will without a doubt get a lot of coverage today, and rightfully so. This is a big deal. The premier RIA platform is now the premier open-source RIA platform.
There are so many reasons why releasing Flex as open source software is a good decision. There has been good coverage already, and the story isn't even that old yet. The bottom line is that, in the end, everyone wins.
By releasing Flex as open source, there is no more barrier for adoption. There is no vendor lock in. There is no reason not to give Flex a try and find out just how great it is for building web applications.
One thing that I haven't seen discussed yet is the public facing bugbase. This is, perhaps, one of the greatest side effects of the announcement.
Currently, there is no public facing bug base. When you submit a bug, you have no idea what it's status is... it just gets lost in the black hole that is the wish form. Through the public facing bug database, you can submit a problem and finally be able to monitor its status. When a fix is submitted for it, you can grab that fix right away from a nightly build or through SVN instead of having to wait months for the next official release. Not only that, but you don't even have to wait for Adobe to write the code. Anyone can submit modifications, enhancements, fixes. You can even fix your own bugs and contribute the goodness back for all to enjoy.
We all benefit from each other's work. We all have a chance to make the platform we rely on daily even better.
This announcement will definitely take awhile to sink in. I know the full scope of it hasn't hit me yet... but I know it's big.
Developers! Developers! Developers! DEVELOPERS!
Congrats Adobe! I'm sure this wasn't an easy decision, but it was definitely the right one. We all win because of it.
Relevant links:

Link lists:
http://weblogs.macromedia.com/jd/archives/2007/04/open_flex_links.cfm
http://weblogs.macromedia.com/jd/archives/2007/04/open_flex_links_1.cfm
I'm sure you get priority service, Darron, but like you said, the wish form seems like a black hole to some people. An open bugbase will be exciting!
Personally, I have submitted several Flex-related bugs to the wish form, and, in many cases, I received a response from Adobe. A couple times, the QA engineer needed clarification. Once, I got a congratulations for finding a particularly good bug. The point is that someone is behind the black hole, and you won't be ignored if you submit a bug.