From experience/reading the forum I would say that IceFaces doesn't inegrate terribly well with other component suites (but discuss this on the Icefaces forum as well), RichFaces should (e.g. we have a Seam/Trinidad/Richfaces example) - IMO this depends on how well the component suite is written. Any issues with RichFaces interacting with other frameworks should be given high priority (assuming it is fixable from the RF end). GWT is another kettle of fish (and a bit orthogonal to JSF) - check out the GWT remoting example for one way to go about using it, and Rob Jellinghaus' work (not in Seam atm) on Seam/gwt4jsf for another way. In general JSF works better than GWT with Seam, as that is where Seam is most used ;)