If you are looking for debugging, your best bet is JBossTools (no, it does not lock you in to
JBoss, it is just a project from jboss.org). It does a pretty good job. However, I will warn you that I don't believe there is line-by-line debugging for a Facelets template like there is in
JSP. Of course, you can use JSP for most of Seam.
RichFaces is quite flexible. It has a lot of "hackable" tags such as jQuery, custom JavaScript function, and other such things. That said, there is a limit to what you can hack with
JSF. If you do too much hacking, you get into trouble. This is discussed in detail in chapter 12.