Currently I have a 12.9” iPad Pro, a 2013 15” MBP and a Mac Mini. I use my Mac Mini exclusively as a Plex and macOS server. My MBP is primary work device when I am at my office. I work in finance and typically have multiple excel models, word documents, and PDF’s open a the same time along with too many safari tabs. For this I need lots of screen real estate which currently only my MBP and dual 34” monitors allows.
When I’m on the go, I find that I am starting to use my iPad Pro instead of my MBP more and more. For writing, I am more productive on my iPad than my MBP because it makes me focus on only what I am writing. I will eventually buy a 5k iMac and use it as my primary device when I am at the office. When I’m on the go I will use my iPad Pro. If I need to access macOS on the go, or want to use a mouse, I will use Jump Desktop to access my iMac and my Citrix mouse (adds mouse functionality when remotely using macOS on an iPad).
iOS 11 has made my iPad a much better MBP supplement, but it’s still not a full Mac replacement for me. If Apple added external monitor and mouse/trackpad support and allowed multiple instances of the same app (other than safari, need multiple MS office windows) I could definetly use my iPad Pro as a full Mac replacement.
It still baffles me that Apple calls the iPad Pro a laptop replacement and then says touchscreen on a laptop is a terrible UI because you can take your hands off the keyboard to touch the screen. A touchscreen laptop would allow users to use trackpad/mouse or touch whereas with the iPad Pro if you are using it with a keyboard your only choice when navigating is touch. If Windows 10 wasn’t as terrible as it is there’s a good chance I would have switched to the Surface Book already.