That's the whole problem. Windows run programs built years ago. Programs that were designed for a desktop environment, not a tablet one. And I don't see any effort being spent to optimise those apps for mobile.
Because that's what Windows 10 is - an attempt by Microsoft to have a presence in mobile by building on its dominant product, Windows (itself a desktop OS). Sure, I can connect a keyboard and a mouse to the SP when I want to get work done, but I have essentially replicated a laptop both in form and essence.
Take those away and what are you left with? A tablet form factor with apps that aren't really optimised for touchscreen usage, which means the user experience is going to be a subpar one. Something Apple solved on day 1 by positioning the iPad solely as a touch-centric device, therefore ensuring that all apps created for the iPad would be optimised for touch and direct input.
The problem here is that the sheer power of Windows is not really giving many people more of what they want, but rather, more problems that they have to contend with. Complexity is not a selling point here; simplicity is.
I feel that iOS has many strengths going for it. It has better security and remains easier to use than Windows and OSX. Likewise, I believe that iOS will continue to get more powerful and fully-featured with subsequent iOS updates, all without compromising the fundamentals that make it uniquely iOS. It's simplicity and ease of use means that users no longer have to contend with all the traditional shortcomings of Windows, and this is a problem that will continue to plague Windows for as long as Microsoft continues to desperately cling to their desktop monopoly and refuse to give Windows the complete overhaul it so needs.
Just look at what Windows is replacing your desktop with. Another PC. Running the same operating system underneath. This isn't Microsoft replacing a horse with a car. This is them strapping rocket skates onto a horse and praying that it can compete with a car somehow.
And the iPad will be that car.
Windows 8 / 10 honestly strikes me as being a very inelegant concept. It's basically 2 different UIs bolted together, and I refuse to accept that such an abomination is the way moving forward.
The question is - what will be replacing the SP once that transition is over?
Microsoft has no answer to that - they are betting everything on the Surface Pro hybrid concept.
The more I look at Apple, I more I think I understand what they are doing. It's the whole "skating to where the puck will be, not where the puck is" strategem all over again. Apple is betting that while the Surface Pro might be seen as the "now", the iPad will ultimately be the "future", and Apple is perfectly content to have their Macs hold the fort and keep the hybrid concept at bay while they manoeuvre the iPad into the desired position.
Of course, the future isn't set in stone, and all these still boil down to how well Apple executes their roadmap. But I do see two things going for Apple. 1) That Apple can afford to wait, and 2) Microsoft has a long-standing history of spectacularly screwing up on the implementation side of their products big time.