I use ProCreate, Goodnotes, Concepts (hate the subscription aspect) and Numbers daily. I've done more studying and better work in the past 2 months than I have in my entire life. For the first time I'm able to make meaningful progress in math. For the first time all of my finances and files and emails and communications are sorted and in order, and not only that, but they are pleasurable experiences now too because the UX is great.
When I share ideas with people I can open Quicktime and pipe my iPad output to it and quickly illustrate ideas on the fly, use it as a wireless second monitor, etc.
I see it as a replacement of the traditional assistant, previously secretary. Siri manages my meetings and emails and reminders, and the rest is just for supercharging my note-taking abilities.
I'm not an apple guy at all, I'm a "don't want to spend 1 second on setup/messing with it" guy and don't care about much else. If Google came out with a suite that functioned better I'd switch yesterday. I've tried every note taking system under the sun. I spent 3 months in a basement inhaling org-mode. Nothing stuck. But I will say there was my life before the iPad, and my life after the iPad. It's a brilliant device. It saves me so, so much time.'
There's really not much else to it besides it being a smooth and fast device that makes even the most mundane tasks like logging transactions somewhat fun.