Xbox one can also be use as a Development kit !

   Xbox one will also serve as a Development kit 

Yes you read it right, even though it hasn't officially been announced in the last Larry Hryb ( Larry Hryb) podcast his co-host Eric Neustadter (e) basicly confirm that the feature will be announced soon 

Microsoft also released a statement a few days ago regarding their vision about the Xbox one 

Our vision is that every person can be a creator. That every Xbox One can be used for development. That every game and experience can take advantage of all of the features of Xbox One and Xbox LIVE. This means self-publishing. This means Kinect, the cloud, achievements. This means great discoverability on Xbox LIVE. We'll have more details on the program and the timeline at gamescom in August.

Personally i think this is great for indie developers and normal gamers who would like to learn and create their own games, something that was very restrictive in the consoles world, what else does microsoft has below its sleeve ? we'll have to wait and see

source Major nelson blog  source polygon