Hello,
I love this software, now that it can show ALL calendars on MacOSX server account and not only the main one. However the real issues on windows is…
you can only share complete calendars in the Server WebGUI.
you can now share selective calendars in EMclient same as iCal…way to go, love it.
however you never get the share invitation in EMclient 
which
cripples it to web interface from the server, also there you can only
see an invitation for the WHOLE account. In emclient you dont see that as
an invitation but under delegation.
So I can share a selective calendar, but it is useless since the user never sees the invitation and can only manage delegations for whole accounts (all the calendars in one account )
So, when will emclient be able to send the user a message, you have beein invited to join calendar “xyz”. this would be the main reason to buy a volume licencse.