I will definitely get this new iPad Pro (have been waiting for this configuration) but this doesn't contradict your point as, for example, I don't intend to plug much of anything into it. Perhaps an HDMI adaptor or ethernet dongle, both of which I already have for my MB.

By the sounds of the usual complaints my use case is quite uncommon (really I need a fast, multithreaded easy-for-demos device for a specific code base the engine of which runs on Linux/MacOS/iOS). It seems Apple is selling a boatload of iPads so they seem to think that few people want to plug things in. That seems absurd when I talk to my friends, but, well, I'm sure the usage data they get from people (like me) who enable that is telling them otherwise.

As for the Surface: I've seen a couple and the hardware looks quite nice but in terms of weight and usability the MBA has been just fine. I often find myself using my current iPad to do something and then put it down and switch to the laptop. The use cases seem disjoint, partially due to the inherent limitations of each platform vs the other in certain regards, so over the years I've given up on thinking that a unified device would be worth it.

I notice people have commented that some of your objections to the iPad have subsequently been rectified, but the core issues IMHO still remain. Another way to put it is that you now can do many laptop-like things on the iPad but it would hardly be your first choice, especially when it's so easy to switch to another device more adapted to things like filesystem manipulation. But if it's the only device you happen to have on your person you aren't stuck. Maybe Surface can find a way over that hump.