David Chappell recently published his Introducing SCA whitepaper, and it is a very good introduction to SCA. I recommend it to anyone interesting in getting a handle on SCA.
In his summary of the effort in his blog he notes the major difficulty he encountered: SCA participants seem to have different opinions about what's important about SCA.
David has blogged about this before, based on his experience charing an SCA panel at Java One. He has also argued (and continues to take this view) that the new Java programming model is what's important.
My view is that the service assembly model is the most important thing, and I guess it's fair to say that IONA as an SCA vendor will emphasize that view as we incorporate SCA into our SOA infrastructure product line.
I don't think the world needs another Java programming model, and although I understand the comparison David makes with WCF, I don't think it makes as much sense for the Java world. In fact the Java world appears fragmented enough already.
I was at Tech Ed '03 when WCF was announced, and I remember clearly hearing the objections to some of the developers in attendance when they discovered that Microsoft was asking them to change how they developed their Web services. And I also agree WCF is a nice piece of work, and has a great architecture (very similar to IONA's architecture BTW).
Our view, and we did express this during the SCA meetings (and we were not alone), was that the metadata should be incorporated into the assembly spec as much as possible, and the metadata remaining in the Java annotations should be minimized.
I suppose it is not surprising that the committee work ended up placing more or less equal emphasis on both the assembly model and on the Java programming model, since the participants in the meetings also represented the division of opinion David encountered at his Java One panel. But this division of opinion continues to be a problem for SCA.