In addition I can say that
Lots of IDE's that support JSF (low cost like myeclipse and intellij idea  with good support and high cost like Oracle JDeveloper 10g,IBM web-sphere studio and Sun java creator with great support)
You can create custom components easily.
Faces-config.xml configuration is easy and besides there is free project FacesConfig."Cool"
You can mix it with other frameworks  like struts,tiles and etc...(faces-struts implementation from Apache Group)
lots of cool components in the standard implementation that make your head spin.
there is the open source implementation from Apache group "My Faces" with lots of components.and Oracle 10g AS supports it's own implementation.
And I'm sorry I have no idea about Tapestry