For the past couple of years I've thought Flex had some clever concepts behind it, but it was going to be collateral damage in the ascension of AJAX. Why? It was too closed on multiple levels. First, to take advantages of its greatest strengths (continuous, bidirectional communication between client and server) required a proprietary Adobe server. Second, the development tools were also proprietary. It's hard to quickly prototype something in Flex, unless you've already made an investment in it. That is poison for innovation. That's also why so much more innovation occurs in Java and PHP rather than .NET, but I digress.
I don't think the above equation has changed with Adobe's new open source initiatives. However, it seems like maybe they are more concerned with competing with .NET/XAML/SilverLight as browser/desktop hybrid technologies. There might be some potential in that, but I still don't think they have the right strategy for it.
Imagine if you were at a mall and you were hungry. There were several hamburger stands in the mall. The hamburgers were pretty cheap and pretty good, and there was a lot of variety. There was one place (Microsoft) that sold hamburgers and fries, but it was very expensive. Now let's say you wanted to sell hamburgers and fries as well. You could make a hamburger and fries that were in similar quality to the sole hamburger+fries vendor, and maybe charge a little less. Or you could make a hamburger that could stand on its merits to the many hamburger-only places, and charge a price similar to those guys. It's riskier, because there's so much competition, but you could still charge a nice premium for the fries. If people start buying your hamburgers, there's a good chance some will splurge on the fries too.
Adobe has chosen to charge a lot for both the hamburger and the fries, just like Microsoft. It's a safer strategy, but with a lot less upside in my opinion. They have to hope that Apollo will lead them to success, because otherwise my original thought will still hold. Flex will be a casualty of Web 2.0.