In case you are not familiar with SlowCheetah, it is a Visual Studio extension which allows you to transform app.config files in the same way that web.config files are. More info on the project page http://visualstudiogallery.msdn.microsoft.com/69023d00-a4f9-4a34-a6cd-7e854ba318b5.
I wanted to let everyone know that I have updated SlowCheetah to support Visual Studio 11 and I have also placed the project on github at https://github.com/sayedihashimi/slow-cheetah. Regarding the VS 11 support there is one known issue that we currently do not support the preview functionality on VS 11. This is an item which we will be fixing for the next release.
Sayed Ibrahim Hashimi @SayedIHashimi
Reminder: even though I work for Microsoft this is a personal project and not formally affiliated with Microsoft