Sorry I am not replying to the original thread with the same name.
I've been working on an HG extension for helping with Rietveld code reviews. The main reason is so that Rietveld can remember state (what issue id is being used) and handle the uploading and downloading to Rietveld. The version I wrote is a little primitive and was written before I fully understood how to use HG. At any rate, I would be interested in participating in creating an hg-codereview extension.