I've noticed some issues trying to create/edit schema-based deployment descriptors. For instance, with the jboss.xml file below, validation seems to work, but code-completion does not:

<?xml version="1.0" encoding="UTF-8"?>
<jboss xmlns="http://www.jboss.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.jboss.com/xml/ns/javaee http://www.jboss.org/j2ee/schema/jboss_5_1.xsd"
version="5.1">
</jboss>

The same goes for the jboss-web.xml file below:

<?xml version="1.0" encoding="UTF-8"?>
<jboss-web xmlns="http://www.jboss.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://www.jboss.org/j2ee/schema/jboss-web_5_1.xsd"
version="5.1">
</jboss-web>

For the following test-ds.xml file, code-completion works but I get a warning about referenced file errors:

<?xml version="1.0" encoding="UTF-8"?>
<datasources xmlns="http://www.jboss.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.jboss.com/xml/ns/javaee http://www.jboss.org/j2ee/schema/jboss-ds_5_0.xsd">
</datasources>

The *-jboss-beans.xml files for the new microcontainer are also a pain, since there's no public schema document available and the namespaces in the XML are all JBoss URNs. It would be a big help if these had tooling support.