The output data is actually clean data derived from OSM. Meaning the nodes of the road will match those generated from OSM. We use a combination of tactics for this including path finding and in some cases this might make the road snapping act oddly, we are aware of this and are going to improve it in future versions, but we decided it was good enough to roll out in a beta version so our users could start using it immediately.
OSM / Google inconsistencies
You might notice as you are using this, the guide layer (represented by a thin blue line) might not line up perfectly with Google. It should line up perfectly with data from Mapbox and OSM.
Depending on how highly trafficked an area is will depend how accurate and close the data is. We should take the time to note that you can contribute yourself at http://www.openstreetmap.org.
Future with OSM
By setting up our own OSM infrastructure this is going to have some great implications for us in the future. Including, but not limited to, the ability to have a totally independent API, our own independent Scribble Maps layers, and the also a new feature to allow you to highlight countries/states etc..