The Arduino language is appreciated for his simplicity, his libraries resources and the huge community around the concept. The programming IDE is also a fantastic tool, easy to use for the newbies.
On the other hand, ATMEL has a free, highly sophisticated integrated development environment with C and C++ from avr-gcc directly available within AVR Studio 5.
It is thus very tempting to associate the simplicity of Arduino and the sophistication of Studio. For example it would be gorgeous to see in the simulator the effect of the program on the outputs, without having to actually build the robot and upload the sketch.
There is a topic from frankDownder here http://arduino.cc/forum/index.php/topic,69822.0.html
and another more developed, from the same auteur here http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=110776
Without these topics, this one would not exist at all and so, we are very grateful to frankDownder.
With a friend of the French forum, we tried to integrate the Arduino language to Studio. We had to modify quite a few parameters of frankDownder (earlier version of Studio ?) but ultimately we succeded. For those understanding the French language, here is the history of our search: http://arduino.cc/forum/index.php/topic,81365.0.html
For the others, you may download a concise but complete pdf summary of the whole process