You're absolutely right that we don't make it clear that you can choose not to use LDAP groups. If you're looking at a pilot and you've haven't gotten very far, I'd highly recommend you check out the Clearspace 1.7 beta. The LDAP part of the setup process has been improved so that we give you an explicit choice between using LDAP groups and Clearspace groups.
Hmmm ... too late.
That sounds like a great feature. When is 1.7 scheduled to be released?