My main issue was that intellisense and even compilation didn't work for SurfaceControllers. Compilation would succeed every time not giving me errors until run-time.
The issue is that Visual Studio thought this was a Web Forms project (wich Umbraco is), but I was working with MVC. I found the solution in this blog post by Colin Angus MacKay at the bottom.
Solution:
To do this, you need to right click on the web project and click “Unload Project”, when it has unloaded, right-click again and click “Edit xxx.csproj”.
Look for the element named “ProjectTypeGuids” and add in the guid:
{E3E379DF-F4C6-4180-9B81-6769533ABE47}
Separate the GUIDs with semi-colon. Then reload the project.
The project is the main Umbraco project (in case you have more than one). You will have to re-set the project as Start-up project after this.
Update: It seems to be a little unstable, as VS suddenly reverted to old (bad) behaviour. Unloading then reloading project fixed it, but hopefully there is a better solution. Will update if I find one.
Note: Umbraco 6 already ships with MVC 4 and has built in support for Controllers (called SurfaceControllers) so the rest of Colin's blog entry is not necessary for Umbraco 6.
Update: When retrying this I found that I had to put the new GUID first in the list. The project refused to load when I put the GUID at the end.
