I've actually got a work Surface Pro 4 with keyboard and blue tooth mouse and pointer. I use it mainly for remote access to my work desktop machine. It's a bit clunky from an interface point of view but it's given me zero issues. Of course it's no more upgradable than an iPad Pro.
I'd have bought an iPad Pro but I got the Surface Pro 4 with all accessories and 256GB SSD (i5) for around $1500, the iPad Pro was $1699 plus accessories but a better comparison would be the work Lenevo laptops vs my MacBook Pro.
I swapped out the screens on the work Lenevos and replaced them with IPS screens, then I swapped out the 1TB hybrid drives and replaced with 512GB SSD drives then I upgraded the RAM from 8GB to 16GB. They cost $999 on special stock and ended up costing under $1500 by the time I was finished with them.
With the MacBook Pro I did... err nothing. Coz I couldn't.
I don're mind paying extra as long as I'm getting extra, with Apple I used to get a longer lifetime which balanced the higher purchase price so the Total Cost of Ownership ended up similar to the Windows machines.
Now though the usable lifetime is no longer than an upgradable Windows machine.
Yes Mac Os is nicer to use but I've got a business to run.
A similar situation exists with the 'new' (but really not coz it's V3 of the iPhone 6) iPhone 7.
Why upgrade when the new phone offers so little extra over the iPhone 6S?
Why upgrade when the new phone takes away a widely used port forcing upgrading of expensive accessories?
Why not cross grade to a different phone with a 3.5mm port?
And I think a LOT of people are going to be asking those questions.