We haven't deployed in about 6 weeks, because this deployment includes a rather sizeable rewrite of the issue tracking system that took us longer than our normal 3 week deployments. We used AJAX to improve the usability of the site in selected places, including in the issue tracker system. We had a lot of feedback on how to improve the issue tracker, so we're very interested to hear how people like the new system!
Just a word of warning, though: this feature upgrade requires an update the TFS work item tracking template for all the projects. It will be several hours before all the projects are updated; while they're waiting to be updated, you might have problems with the Issue Tracker on projects, and the TFS server may be slow for all projects in the interim. Please be patient while we get the TFS server template upgraded over the next few hours.