Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, to please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

are the Xor methods really necessary? Where do you expect them to be used?

I see some unmanaged usage with regard to job scheduling, but the scenarios for this (at least in C#) don't seem as clear-cut as the scenarios for And and Or. I'm not going to be terribly sad if we decide to nix Xor. It was really just for logical operator completeness.

I'm not going to be terribly sad if we decide to nix xor

Ok, I'm going to remove it. I want to add things only when there's a strong demonstrated need, and I'm not seeing that for xor.