Read: Introduction to JBoss Seam.
The article is an editted excerpt of chapters 1 and 2 from the first (to-be-released) book on Seam by Michael Yuan and Thomas Heute. It explains what Seam can do and grounds the concepts with a HelloWorld example.
In his interview, Gavin King told InfoQ that Seam has been well adopted within the JBoss community and is recieving over 5000 downloads a month. One reason it never got far out of the JBoss community is because Java EE 5 support is not yet widely available across the appserver ecosystem, which is why the EJB 3 dependency was made optional in Seam 1.1. Gavin King will also be presenting Seam at QCon London, March 14-16.