I've been getting a lot of requests for comments on this subject and I'll be brief. As I think it's a politically hot topic and I don't want to get into that level of discussion (no good can come from it).

1. Flex SDK was free anyway.
2. Flex compiler is now free for all to use. That being said in the past, projects like http://osflash.org/swf was always there? I mention this as I get what they are doing but I only see this as being a way of leaning on the community to do more for them, and to be honest, enough already :) you've asked too much as-is.
3. Entry barrier for FLEX hasn't changed, people still need to scratch their heads and figure out how to go from no idea what ActionScript 3.0 / MXML is to learning the code base and then figuring out how the framework gels together. It's good but keep in perspective, the game hasn't changed just the playing field is no longer concrete, but grass (fertile growth is where I'm heading).
4. Why stop at FLEX the language, I think the real room for innovation should be around Flex Builder 2.0.1 (FB) so if CFEclipse + FB were to marry, that would be some taste stuff.
5. Server-side pieces are still going to be a price hurdle and I don't foresee that changing (something's got to pay the FLEX Engineers bills day in day out).

I think it's positive and gutsy approach by Adobe, but at the same time I'm not sure whether the community carry it forward, as they're busy still learning the individual pieces (getting better daily) but this is a long term investment and when I read posts from Adobe staffers like "Sho" where they say the word "hope" - I get nervous. I also think the community have done enough already, so I'm not subscribing to the approach of slapping a post-it note on the side of FLEX and say "DIY GUI, you do better". (I've been wrong before so no guarantee's I'm right on this one)

I see both positive and negative pieces to this story, and the real pressure will be on Adobe in terms of steering the project in a direction that's universal. I think one person today said "Once you open source a project, there is no undo".

In the spirit of MIX07 Vegas, Adobe are essentially "Letting it ride, double or nothing"... (Which is just super for a few friends of mine in cubicles right now hoping to hell Flex risk they took pays off).