The visual studio object browser simplifies browsing of arduino/wiring libraries, custom libraries and your own code.

Editing any of the ardupilot versions using visual studio 2010 really shows off the quality of the ardupilot code. I love people who comment their code. Very neat!

And look how easy arduino project "navigation" is in Visual Studio, you can "Go To" the right place in the code.

I didn't know where the stabilize() function was but visual studio "Go To Definition" took me right to the attitude.pde. The intellisense in visual studio works best with well stuctured programs such as ArduPilot!

You need Visual Micro to make this work easily in 2010. It is free and quite new so the help system is a little confusing. Feel free to grab a copy.

The ardupilot code can't yet be compiled in visual studio due to the complex interaction between the multiple .pde files. However, Visual Micro adds a menu item to visual studio called "Open project in Arduino".which allows you to easily jump into the Arduino IDE to compile your mods. The next release of Visual Micro will allow compile and upload from within visual studio

The initial release of the visual micro addin for visual studio is designed for arduino however it should be possible to use the system to program normal avr devices using visual studio. This is entirely untested but at the very leat this software will provide all the information and tools you need to adapt an avr solution.

Ignoring the arduino boards and library system you will find everything you need to adapt your own Visual Studio avr solution. AVR Intellisense, compliation, upload and much more