I have deployed XWiki with LDAP authentication and group mapping. However I had problems getting group mapping to work. The reason for this was that there is case sensitivity in group member discovery.
Let's say I have users in ou=People,o=ACME. Let's say my dn is uid=GregC,ou=People,o=ACME. Let's say I my groups are located in ou=Groups,o=ACME. And let's say have a LDAP group cn=XWiki,ou=Groups,o=ACME. My XWiki group is of objectclass groupOfUniqueNames and contains uniqueMembers.
If in my XWiki group I enter
(note lower case in o=...)
the group mapping mechanism will not work. If I change "o=acme" to "o=ACME" it starts working.