The developers of Seam have come up with a list of major issues with JSF. I'm assuming many of these issues are fixed by Seam, but it's interesting to note how they've somewhat admitted that JSF has many flaws. Note that there's a lot of references to Struts and WebWork.
Hopefully many of these will be fixed in JSF 2. If REST support is an important feature for web frameworks, it'll be be interesting to see how the component frameworks handle it. It'd be great if they provided native support. Oh wait, then they'd be action-based frameworks.