I successfully installed the Domain Mapping plugin (v2.1.1 on WPMU 2.9.2) and all has been well.
However, since installing, whenever I create a new blog (subdomain) it appears in the blogs list in the WP Admin area, and an entry is created in the wp_blog table. I did notice that no other tables matching the new blog ID exist - not sure if those only get created once the new blog is accessed via the backend, or if they should be created when the blog is created.
Nevertheless, any attempt to visit the new subdomain - either frontend or backend - results in a "server not found" error.
Wildcard DNS is in place and hasn't changed on our server.