It would be convenient to allow for the download of the diff file during a pull request.
By this I mean, it would be nice to have a button that when clicked, would download a file summarizing the diff that could be opening in standard diff tools locally to further examine without having to be online/connected to Stash.
This could help during very large pull requests where one could review the PR offline, recording their comments locally, then "upload" all their comments when they get back to the office.
It would also allow those who want to use their own diff tool to easily download and open the diff locally.
Code Collaborator provides this functionality as documented here: http://support.smartbear.com/viewarticle/20126/