I upgraded to openldap 2.4.6 recently and converted from the slapd.conf file to cn=confg and slapd.d directory. The bottom line is the directory config is now controlled through the directory service rather than the config file and config changes are dynamic, happening immediately rather than requiring a directory restart.
(I guess in this sense,it caught up with Active Directory although that comment would be argued fiercely on the openldap list.)
The switch to a /slapd.d-based config is straight forward. You can feed the slapd.conf file through a conversion process by using one of the slap utilities,
slaptest -f /etc/openldap/slapd.cong -F /etc/openldap/slapd.d
will create the cn=config structure and create the various ldif files that control the frontend, config and backend databases.