I can't find any description of IOperationResult or any of its subclasses in the .NET docs.
I can find a pretty decent description in the wiki, here:
That info needs to be in the manual. Also, the return value for an operation is critical for understanding what it does. The API summaries elide the return value, and make it difficult to understand the function fully. It's worth the extra screen real estate to specify the return value in all the API summaries.