Meh. I'm more productive when one thing has focus, so I prefer not having multiple applications open at once vying for my attention. One display works great for me ... I'd even shut my laptop screen if I could, but I use touch ID for authentication.

Maybe it's a failure of imagination on my part, but I've never been in a position where I thought that having more screen real estate than a large 4k display would be helpful. When I need to have more than one application visible I can do that; when I want to focus on one thing at a time I can do that too.