This forum is now a read-only archive. All commenting, posting, registration services have been turned off. Those needing community support and/or wanting to ask questions should refer to the Tag/Forum map, and to http://spring.io/questions for a curated list of stackoverflow tags that Pivotal engineers, and the community, monitor.
Most users should be able to upgrade without any problems (for example, nothing xml or action related is incompatible), but yes there are some backwards incompatible changes--mostly name tweaking and package moves (for example, flow execution listener moving to web.flow.execution).
We'll be sure to note them in the release announcement.