Battery life is probably gonna be real bad. Dave2D said the lowest cTDP the APU can do is 15W, up to 30W at the highest. That would drain the battery in no time.
Also have you seen the cooling system? 4 heatpipes and two fans, this is designed to draw loads of power. In my opinion misses the point of the formfactor.
No real competitor to the deck.
Well, we paid probably what the case costs for valve to make... so like 3$ maybe..? Id say that is pretty much "for free"