I'm using the Changeset REST API (http://confluence.atlassian.com/display/BBDEV/Changesets). The pages are sorted descending but the results within a page are sorted ascending. So the first page of changesets are the most recent, but the first changset within the json result, isn't the most recent. I would have expected the changesets within a page to be sorted descending as well.
Let me know if you need more info.