Multivalued columns can be very useful for simplifying data schema and improving performance, but they can be complex to use (they also make Data Normalization geeks feel uneasy). I put a multi-value tutorial up on the ManagedEsent wiki. It uses the managed APIs but would be easy to translate to unmanaged code.

http://managedesent.codeplex.com/wikipage?title=MultiValueTutorial