I think you bring up some good points. However, personally, I believe if I had to go on frequent business trips where I needed to do a lot of typing on the road, I would go for a MacBook Air + iPad combination. Yes, the total cost of two items of hardware plus Windows plus Office would be a lot more than a single Surface Pro. But I'm not convinced that the Surface keyboard covers provide a good typing experience. They are somewhat smaller than regular keyboards, while the Air has regular sized keys. And when you take off the keyboard cover and use the Surface as a tablet, you end up with a heavier and bulkier tablet than the iPad. Especially if you go for the iPad mini, there's just no comparison.
The Surface Pro, IMO, provides a compromised tablet and laptop experience, but you only have to carry a single device. I prefer having a good tablet and a good laptop, even if it means I have to carry two devices. Of course, that's my personal preference, and I can understand how other people might prefer having only a single device to carry.