A migration guide from JBossWS 3.4.x to JBossWS 4.0 (and in particular to AS7 w/ JBossWS 4) should be included in the release documentation.
At the moment the topic to be covered should be:

• consequences for users due to changes in classloading (see JBossWS AS7 FAQ)
• changes in API (new jbossws-api library, package refactorings, etc.)
• @WebContext(virtualHosts) -> @WebContext(virtualHost) change
• changes in WS-* configuration
• changes due to libraries upgrades (mainly due to dependencies coming from Apache CXF 2.4 upgrade)
• new descriptor(s) (jboss-webservices.xml)