Yep it would be good, i've been trying on and off. I can't get avr studio to recognise any addins at all. Failed at the starting post!!

If you look in the vm install files you will see .addin files. 

.addin files are xml files that contain tags specifing which vs version to run in. 

I tried "Avr Studio" with a version of "5.0" which didn't work. So i tried the internal name and version of the avr studio exe. That didn't work. So I logged a support request with avr who wrote back saying they are not sure but "Avr Studio" and "5.0" works for vs extensions.

Instead of guessing where to put/test addin files for avr studio you can add a macro search path via tools>options>macros.

The Visual Micro addin uses the Visual Micro Arduino Api for the compile, upload and also to get lists of included libs, boards etc. The api only needs the name of a sketch.pde to compile and upload. So the visual studio side of the addin doesn't do much more than the following:-

1) add menus, bars and buttons
2) alter visual c++ project properties for include paths for intellisense
3) add and maintain .sketch.vsardiono.h using info from the api
4) capture (and selectively override) window,project, projectitem, solution and dte events
5) show output messages, serial window etc

Making an addin work might just be be the tip of the iceberg. There doesn't seem to be much information published by atmel about extensibility support.

In vs 2010 we can switch boards/cores for intellisense just by altering the C++ project includes. In avr studio they have their own language and hardware extensions which do not use the C++ system. 

Avr Studio appears to have avrC and avrCPP lang extensions. I can't find any information that would show how to switch cores (when a board is selected) in avr studio but it might just be a matter of making the vsarduino.h file. Avr studio has its own board properties which I am guessing are fundemenatal to the intellisense. We need to know how to program these properties via a package or a macro.

If an addin did work in avr studio we might find the properties that we need via the debugger but the lack of documentation makes it difficult for my pea brain.

If anyone would like to help with the project then I'm game