August 2017 update: I just noticed the tech specs on the Arc Hub product page have changed to read: "Arc Hub comes with 1 x Mini Display Port 1.2. Capable resolutions are all HiDPI resolutions, 1080p@60hz, 2560 x 1440 @ 60hz, 3840×2160@30hz." The tech specs used to mention 4K at 60Hz 🤔.
original tl;dr: A capable hub, with some slight design flaws. However, not yet recommended if you want to use it with a 4K monitor, due to compatibility issues with higher refresh rates.
When I bought my 2016 MacBook Pro, I expected a lot of changes. Since I picked the function key model over the more port-laden, but much worse-for-me Touch Bar model, I knew that there would be some
growing shrinking pains, going from a generous assortment of five ports on my MacBook Air to two (!) USB-C ports on the MacBook Pro.