This is problematic. Netscape Calendar logins are Firstname Lastname instead of a username. Middle names are not supported in Netscape, so managing users with the same first and last name is very confusing. Usernames would solve this problem, too. This is a nice feature.
Resource calendars for rooms and equipment are a necessity.
A search feature would be nice. Migration is always a nightmare. Integrated migration tools from Netscape Calendar would be nice. Permissions on individual calendar entries is a nice feature. Manually creating accounts is a drag.