Working from home today so I propped up my Pro and used Duet to set it up as a second monitor for my MBP. Works like a charm and the screen is almost the same size as the laptop's:
I wish the thing were less expensive (which I wish about many of Apple's products) but it can be quite a versatile device (not that other versions can't but the large screen size helps, at least in my case). So far, I've used it as a standalone tablet, as light laptop replacement, second monitor, and graphics tablet (via Astropad and native apps with Pencil).
I was thinking, if I had to travel a lot for work (I don't), a laptop + iPad Pro would be a perfect combination. During transit, keep the laptop stowed and use the iPad for whatever work or entertainment I want. Wherever I'm working, use it as a second monitor and do the heavy work on the laptop. Back at wherever I'm staying, stow the laptop again and just use the iPad unless something needs serious work and then bust out the laptop again.