I think you have to go into the Network Sharing and Discovery Center, define
your workgroup as a private network, then turn on all those sharing and
discovery options.
Also, you may have to go into System and change the default workgroup name
from WORKGROUP to your actual workgoup name.
Finally you may have to manually add any shared printers through the
Printers dialog.
I'm not 100% sure that all this is correct because I haven't looked into it
alot, it's all been so shaky through the builds. But I did manage to get
everything working through the above means in the last couple of builds.