i'm a designer working from home in my spare bedroom/converted office.
i use my stupidly powerful pc's for all my design and rendering work. i have no choice in the matter.
but i too need to supplement this with general office duties/admin facilities.
What the 12.9 Pro, Pencil and smart Keyboard does for me on a professional daily bases is OUTSTANDING in doing so.....
1) all my emails and email accounts.
2) all my diary and appointments and meeting times.
3) Skype and messenger facilities, including facebook and social media accounts.
4) notes - all my telephone notes, conversation supplements, sketches, etches, to-dos, ideas etc etc are all recorded in Notability. i probably make pages and pages and pages within a week.
5) Pages handles all official correspondence, invoices and letters to clients via my own templates.
6) Numbers happily copes with my accounts and XL sheets. again, custom made templates.
7) Safari - banking and general comms to the www
8) Dropbox is my off site storage
9) Prints everything beautifully to my wireless laser copier.
and a few minor other apps that do various small tasks.
But in essence, the 12.9 Pro has completely changed and streamlined my working pipeline for the first time in well over 25 years of doing this ****. For me to say it's a game changer is putting it mildly. I dont use my ipad for anything leisure or no-work related usually, so gimmicks and gadgets are not important to me. the screen and processing speed is my god.
In my opinion, if you want general office/admin facilities and are not too worried about not using desktop software or the same software you're generally used to then you cant go wrong with Pro as an office companion. So far there's nothing it cant do for me in this capacity.