I am using JSF on an existing application for a big company. The existing application has several hundreds of JSP files filled with scriptlets and business logic, needless to say there's a lot to be done.
So right now we're formulating a new more sound programming model that will result in more maintable code, by using jsf for the presentation layer and business logic placed behind a web service layer.
I am using JSF to redesign an existing large (thousand of pages) client-server commercial application for a big company. To speed and simplify the redesign process of the user interface, originally developed using a RAD tool (PowerBuilder) we have developed a large set of custom components (some new components and many extended ones) to emulate those used in the legacy product.