mapping domains and www. Does it work?

This may be a follow up the a previous post.

https://premium.wpmudev.org/forums/topic/unable-to-utilize-www-in-subdomains

Is this still the case? If so, What or how should domains be set at the registrar level for A and / or cname records?

I am trying to get my sites working with ProSites and Domain mapping. I have my multi site set to directories.

Louis