Before the 6D existed there were calls by many enthusiasts, some on this forum, for a lower cost simplified full frame camera, some even called it a full frame rebel. According to a canon factory rep I spoke with thats the driving force behind the development of the 6D. The user interface, while not quite that of the rebel, is more rebel like. The lack of the PC port, the slower top shutter speed, the slower sync port all point to where canon wanted to position the camera in their lineup. Below the 5DIII so as not to cannibalize their own market base. However the improvements in low light performance and the improved outer focus points make it attractive enough that many users want it to be a full featured pro camera. The canon rep summed it up like this, "they asked us for a full frame rebel, we gave it to them, and now we are getting killed for what we left off."