This really needs some attention, see this thread and this google issue for full details.
Spring Webflow contains a simple sample app, booking-faces, which works well with PrimeFaces 2.2.1, but fails with PrimeFaces 3.X. I've tried it with the latest Spring versions as well, in which PrimeFaces 3.X still fails. It seems somehow to step on the webflow context.
The sample apps all demonstrate this clearly, and may be found here.