One thing I noticed is that is has its own idea's of interpreting LDAP standards.
I once ported an application (IBM accessmanager) to Siemens Directory, and I had a lot of problems due to the generalizedTime syntax, which is incorrect in IBM. (timestamps look like 20030819230745.Z, beware of the point!)
Checked this moment on a public IBM Directory Server 5.1:
createTimeStamp: 20030628025321.000000Z
Hmm, isn't that valid GeneralizedTime syntax with fraction of seconds?
Ciao, Michael.