I am actually not too sure that the DIGITS app for PC has the capability of being set as a default dealer like Skype can be set. This is a great suggestion though and I will be sure to get this idea sent up to the dev teams. Who knows? We might see this kind of functionality in future releases.
Yes... This definitely would be a nice feature.
However, Skype is a Microsoft product and you know how they are... the main reason my "primary" computer is Linux.
There is a similar opportunity for DIGITS. A number of headset manufacturers recognize installed software to work with. For example, I have a Sennheiser headset that doesn't support DIGITS. I certainly don't expect it to at this stage of the game! But now would be the time the developers should be looking towards business products. I know most folks don't have a $350 headset at home, but maybe they would at work. The point being is, again Microsoft Skype is again my only choice. Imagine an incoming DIGITS call on your PC and pressing a button on your headset to answer it while you are in another room.
...just a thought. Might be a bit early for feature requests. :-)