I think Jeff is being conservative (that said, Jeff and I work together at Adobe, so no lack of bias here -;). Thanks to network effects, the adoption curve for a new technology is exponential, not linear. (eg. It is much easier and faster to go from 1/2 a million to a million than from zero to 50,000.) We've had something like 150,000 folks download and try Flex since we launched the Flex 2 public beta. We have an active community building real apps of tens of thousands today. (There are over 5000 I believe now on a single mailing list, flexcoders). We have a lot of very high profile apps coming. The release of Tamarin last year, Apollo this year, some upcoming new technology, 6 new books by O'Reilly alone, will all draw in new folks.
The best sign for me that viral organic uptake to get us on that exponential curve is happening is a conference called Flex360. This is a full multiday conference on Flex and it was organized and hosted by eBay, not by us! The conference sold out 400 spots six weeks in advance of the event. The day it sold out, by chance, a company in Washington DC announced their own Flex conference for June. This stuff is happening now more and more around the world. (We had 2000 people at an event for Flex recently in Korea!)
I think we'll exceed these expectations.
What do you think of Flex yourself? If you haven't tried it, this is a good place to start if you are coming from a Java background: http://coenraets.org/blog/2007/01/flex-test-drive-server-for-java-developers-tomcat-based/
Let me try again...I hate to be accused of "hype" -;)
We are not claiming we have a 1/2 million developers. That is an extrapoloation that blog author made. I disagree with that. My assertion (based on a bunch of data sources) is that we have about 150K who have downloaded or tried Flex and 10s of thousands active developers. That is not 1/2 a million, nor a million, but it is a great start for a product that we shipped 7 months ago and I believe a sufficient start (but not a guarantee) for us to hit the goals that Jeff suggested in the article. This is not all marketing "hype". There is a pretty deep body of data on the developer community, # of developers per region, by language, by application type, etc, from companies like Evans Research based on statistically valid surveys of developers around the world. Here at Adobe (and those of us who come from Macromedia, or even Allaire before that) have a lot of experience building such communities. We have an active community of about 300K ColdFusion developers, well over a million Flash designer/developers, and several million Dreamweaver customers as well as folks on the team that led the creation of the .NET framework and key parts of Java/JSP. We've tracked these kinds of trends and adoption rates before. That said, past results give us insight into how an adoption curve *could occur* to meet our goals, but the rubber will hit the road on how well people like Flex and whether it solves real problems for them. So far, the trends are good (from our perspective) but the real question I have for you is what do you think of Flex, rather than what do you think of how successfull Flex is? Time will tell on the later.