There are some minor differences in the repository metadata generated by Maven 3 vs. what was generated in earlier versions of Maven. This can cause some strange install/deploy errors if you use two different versions of Maven to deploy snapshots of the same project. For example, if you use Maven 3 to deploy a snapshot, and then use Maven 2.0.9 (or earlier version) to deploy another snapshot of the same project, you will get an XML parse error.
expected START_TAG or END_TAG not TEXT (position: TEXT seen ...<extension>jar</... @13:25)
Fortunately, this only has an effect if you are using two versions of Maven deploying to the same location (groupId, artifactId), and it's only if you are using Maven 2.0.9. There is also a workaround which is to use the Maven 3 property maven.metadata.legacy.
mvn deploy -Dmaven.metadata.legacy=true
It is recommended that all JBoss projects use Maven 3.
There is a note about the metadata change in the Maven wiki