A nice improvement to the process of adding revision(s) to a review would include the ability to search by commit hash.

In our agile process, a "story" that is ready for code review generally has the last commit hash (or a list of the commit hashes) documented somewhere on the card/case/whatever-you-call-it. Given this information, it would be really nice to simply copy that hash and be able to search for revision(s) when starting a new review.