If you have had Visual Studio hang when editing a testsettings file, please vote up my feedback to Visual Studio.
http://visualstudio.uservoice.com/forums/121579-visual-studio/suggestions/5921100-improve-testsettings-editing-dialog-so-it-runs-dec
I run into this every time I have to update a testsettings file or change some properties on the Vm test agents.
Thanks,
Kevin