The release is mainly meant for JBoss Application Server 7 and has been tested against AS 7.0.0, 7.0.1, 7.0.2 and the current 7.1.0 snapshot. JBoss AS 6 support is still included, but might be removed by the time JBossWS 4.0.0 goes final (hopefully soon).
This is really the right time for giving JBossWS 4 a try before it goes final! Any feedback is welcome and might turn into last minute fixes for major issues, if any ;-)
Meanwhile we're working on passing webservices-related tests of the full JavaEE certification testsuite using JBoss AS 7; JBossWS 4.0.0 final is going to be shipped in the final AS 7.1.0 release.