T4MVC Known Issues
Errors when using VisualSVN
Users running VisualSVN have reported some errors when T4MVC tries to change actions to virtual and controllers to partial.
The suggestion when that happens is to manually make those changes. This is just a one time thing you need to do.
Controllers living in different projects
T4MVC will not locate controllers that live in a different project or assembly
Async Controllers are not supported
See this thread