I've used older iPads with an old Apple bluetooth keyboard and it's amazing how useful they are as a notebook replacement. Keyboards and Pens have been part of the iPad 3rd party eco system from nearly the start. The iPad Pro formalizes what many iPad users have been doing all along.
The only issue I have open with using the iPad Pro is: How will it work with an external display. I really enjoy my 27" display when I'm at my office. My gut feeling is Apple will address this with the next revision, but who knows if there is an adapter cable in the works...
Read this:
http://www.technologytell.com/apple/143054/ipad-mouse-support-is-desperately-needed/
Apparently I needn't have written all that, I could have just cited "Gorilla Arm".
What I'm saying also is that any iPad plus even the lightest keyboard is pretty heavy (0.84lbs) There is no weight argument to be made in a world where 13" laptops weigh as little as 1.72 lbs. It is not a good notebook replacement when it cannot even be rested on a lap. It needs a stand to even rest on a table in way that a human being can see the screen. You need to carry both a stand and a keyboard for it.
But maybe there are a small number of users who must have iOS over Mac OS or Win 10 and I suppose the product will fill that very tiny IMHO niche. Especially in a world with $200 Chromebooks.
Apple has had some very boneheaded restrictions on iOS that even this "pro" version doesn't address. Where is the mouse support? There is a huge difference between having to input on the screen on the device or having the option to have input from a distance with a mouse. It is disgraceful for them to release a "pro" device without that capability that every other OS offers.
To your point about displays the fact Apple that does not support Airplay to and from Macs and iOS devices is also very stupid. This prevents me from using my 27" Retina iMac as a display for any iOS device. Add to that the next Apple TV won't support higher than 1080p precludes any use of a 4k or 5k external display for iOS devices. It might have been nice to Airplay iOS retina content to an Apple TV. Let's not forget that wired connections to the iMac Retina are not possible because it does not work in target display mode at all. Couple all that with the lack of a 5k cinema display and I don't understand what method there is for an external display beyond 1080p Airplay or wired via displayport adapter to a legacy display or iMac.
On top of all this you have people going ga-ga over Microsoft Continuum like it's the next coming. I laughed to learn that it still relies on a wired connection to the display. This is because for last 3 years or so I've been hearing Miracast, WiDi nonsense and supposedly my laptop supports this technology but not once have I seen it actually work.
Meanwhile Apple has perfected wireless display, it works amazingly well with the Apple TV. I have no doubt that the technology for Airplay up to 5k is present in modern Macs and even iOS devices. Airplay at 1080p has been functioning for 3 years on phones with hardware several magnitudes lower than what we have now.
Through artificial restrictions such as no mouse drivers and lack of Airplay to Macs they have gimped this supposed "pro" iPad and for that matter all iPhones and iPads. If those features were enabled it would be basically Continuum with wireless display. Which of course makes it far superior to Continuum. Even with Continuum developers have to design and implement this mouse driven UI on a per app basis - it isn't the full Win 10 UI at all. There is no reason an iPhone could not just be in your pocket while you sitting in front of your iMac and using it with your existing wireless mouse and keyboard. Very boneheaded by Apple. It could have been a Continuum killer.
In observation the best use for iPads and tablets in general is commercial. They are great in restaurants for wait staff to use in table selection and order taking or in gimmicky places for customers to pick wines or menu items. There are great anywhere a business needs to interface with customers such as check in at doctor's offices or self serve kiosks of any kind. They are an amazing tool for lots of commercial applications and we'll be seeing them at more businesses. They are best used for short periods by any one person.
The Gorilla Arm issue is real and it explains the declines in the tablet year over year over year. Apple just managed to make tablets gimmicky enough again that millions of fools (myself included) bought them. Lets face it for many decades we've heard about handwriting recognition or voice recognition as the holy grail. We thought these technologies will kill the keyboard. Even if perfect handwriting recognition came out today anyone doing input beyond writing a sentence every few minutes will prefer a keyboard. Even if perfect voice recognition came out today it would take a cultural revolution to see people talking to devices as their only input method with it. Of course there will niches but none of these technologies will be the basis of a "game changing" product. The best input method outside of a keyboard would be neural recognition wherever that happens.
Back to the present if the tablet form factor were sufficient for my needs and ergonomic situation I'd still say if Microsoft sold just the tablet half of the Surface book it would be IMHO a far better device. Win 10 is just a more capable than iOS. iOS is nice but you have to admit it's old now and new functionality just gets tacked on. It's often buggy these days and when I take my iPhone to Apple Store for running slow or eating battery they run some test and say processes are crashing. They tell me clean install iOS meaning I cannot restore from any backup. It is no different from the days you had to reinstall Windows 98 every few months. I can assure you Win 10 is actually far more stable than what iOS is becoming.
iOS needs a fundamental rethink from basic ergonomic principles. The back arrow is on top left of a screen is in a place that is impossible for many to reach while holding the device with one hand. The home button double tap is just a bad way to access the app switcher. 3D touch as it stands is a great concept that is so half baked in it's implementation that it seems like a placeholder. The feature is revolutionary but they couldn't be bothered to even outfit the apps that come with the phone, that cannot be deleted, with functions for this feature. I still love my iPhone and my Macs but I can't help but point out this company is not operating at the level it used to.