At work, we've just moved to using OpenDS over OpenLDAP for a few reasons, including (off the top of my head):
- Virtual attributes and plugins available in the base build to handle lots of common cases such as group support, referential integrity etc. with minimal configuration
- Platform-independent Java implementation, alleviating our need for native binaries
- Out of the box SSL-enabled connection handling, with Java keystore support
- Good, centralised documentation on the wiki and the configuration guide
- Very responsive team on the mailing list and IRC
I should also add it's really easy to try out - there's a Java Web Start link that can get you running almost instantly and the zip download has everything you need, provided you already have a JRE.
Thank you to the OpenDS team for a great product!