How well is Seam development supported by various IDEs? Are good tools being made or are available on Eclipse and NetBeans? Are free of cost and supported ones around? As far as I know, JBoss IDE has something here, right? How helpful are these and does your book cover their use to any extent?
JBoss Tools has quite a bit of support for Seam, code complete in the EL, generators, built in palate support, graphical layout of pages.xml, etc. Netbeans tooling isn't quite there yet. Netbeans has support for JSF and facelets. Seam-gen (if you're using it) is simply an ant file so you can get some support in Netbeans that way as well, in fact when you generate a Seam project with seam-gen it creates the Netbeans and Eclipse projects for you.
IntelliJ has some awesome support in Diana, on par (and better in some ways) with JBoss Tools. If you're an IntelliJ user and are using Seam you should check out the Milestone 1 of Diana aka IntelliJ 8.
Jason, again an excellent summary. I want to start by saying that, just as I recommend in chapter 2 of my book, the seam-gen script goes a long way to getting you setup without needing to lean on an IDE. You can then import that project into an IDE and do the typical Java and XML editing that you would normally do. The question then becomes, how well is all that extra stuff supported (i.e., EL completion, Facelets tag completion, acknowledgment of Seam components).
Being a Seam guy, you probably expect me to push JBossTools. Of course, JBossTools is going to constantly push to make JBoss software integrate well. But after seeing the video and playing around with the Seam support in IntelliJ IDEA 8, I am truly impressed. Seam is the number one bullet point on their feature list and it shows. Here is a link to the video. See for yourself.