It runs full windows.

Allow me to repeat.

It runs full windows.

I'm a grad student. I have a workstation in my office. But at home, it's perfect for reading research papers thanks to the high resolution display, the fact that I can disconnect the keyboard, and the included pen which I can use to annotate.

Yes, the iPad can do all that, but I can reconnect the keyboard, and continue using Matlab, or log in remotely to my office machine and continue my office work, or edit spreadsheets/PPTs/thesis in full MS Office. And it's light enough that I can throw it in my backpack "just in case" I need it. Honestly, the being able to disconnect the keyboard thingy seems gimmicky before you get used to it. After you do, it's a godsend.

There's a hell of a lot more "windows apps that weren't designed for a tablet" - 20+ years' worth - than there are "iOS apps". And not just apps but also a lot of hardware peripherals. I play '90s games at lan parties (which aren't really substitutable - iOS might have strategy games, but it won't have Supreme Commander and that's what my friends are playing). I run eclipse (is there any kind of Java IDE on iOS?). I run the vocaloid software (which iOS doesn't have, though it might have other music synthesis software), and the fan-made 3d modelling software that people use to animate the characters (which definitely won't exist for iOS); I render and encode the resulting video. If a program hasn't got a windows release I can compile it on the surface itself and run it there (can iOS do that?). If I want to run a program for a different platform I can run an emulator on the surface (which the iOS app store disallowed last I knew).

How many non-crossplatform apps does iOS have? How many of those don't have acceptable substitutes for at least most use cases?

It's an excellent development environment for everyone but iOS and macOS developers. It's got a great set of digital illustration tools with a lot more time put into development than the newer iOS equivalents. It's is a full windows box, which gives it impressive range. It has better linux binary support than MacOSX (unfair, that has none).

There are a lot of windows apps that are designed and work really well on the tablet. It's not like Apple holds a monopoly here.