@melgross, good point about sales, I feel that sales are not skyrocketing because, technology (CPU price, performance and power consumption levels, etc.) has not reached the level that the Surface category desires -- it is a new category as many other manufacturers are also rolling out products that are similar to the Surface Pro.
Microsoft might be utilizing its capital strength by remaining in this category until, technology reaches a level where hybrid devices are economical or it might have already reached the desired level with the Surface Pro 4.
Either way, innovation is taking place. It is apparent as we see a Continuum transform a mobile phone into a PC.