It concerns me a little that the Struts 2.0 (Shale) proposal is tied to the Servlets 2.4 spec. I'd prefer to see it abstracted away from the servlet spec so it could provide better support for Portlets.

One day I mean to write about how annoying the Portlets spec is to integrate into an existing MVC framework because of the way it already has its own semi-MVC API (the do* and processAction methods). It is possible – the Spring Framework portlet support has had a few more advances since my patches – but generally it makes it difficult because of how tightly most frameworks are tied to their own dispatching mechanisms