I pulled in OpenLDAP 2.4.9 to re-visit some multi-master testing I had done on the previous version. 2.4.9 was a better experience for me than 2.4.8. I re-ran some tests of running two replicated servers on the same machine. I would continuously load in several hundred or thousand user records on one server, then delete them.
The stability is improved from 2.4.8. I have yet to have a server core on me--even after abruptly shutting done one or both servers during a batch load or delete.
My only issue now is that when performing a bulk load, if you interrupt the client during the load ( Control-c ldapadd ) the servers get out of sync. The server you directly attach to in order to load the records contains more records than the "replicated" server. Under most circumstances, this would not be a huge issue, but it does show an easy way for a client to get the servers out of sync.
With the 2.4.9 release of OpenLDAP, I would trust the multi-master synchronization enough now for use on production systems.