The get goal does not pass the server credentials from settings.xml to the BasicRepositoryConnector in version 3.0.1 (and, presumably 3.0.0), resulting in NotAuthorized errors when resolving artifacts against repositories that require authentication. It works correctly in version 2.9.
Background: I discovered this in the course of debugging a Jenkins job in which I'm using the get and copy goals from the command line (with no POM) to download artifacts to deploy. After spending several hours thinking that Jenkins was not properly configuring settings.xml, I noticed from the Maven debug output that the credentials were being passed when resolving the maven-dependency-plugin and its dependencies, but not being passed when resolving the artifact I requested. On a hunch I downgraded from maven-dependency-plugin version 3.0.1 to 2.9, and suddenly everything magically worked.