What I have set up is wordpress mu with the multisite add in. This allows me to set up blogs as subdomains, but currently I have to edit the vhost file manually at the end of the process to make it point back to the wordpress mu directory containing the php.
No manual editing needed. What you did is exactly waht the subdomain is for. Just add as many subdomains as you need and they will all point to the wordpress mu installation of the master site.