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, [email protected], 2560 x 1440 @ 60hz, 3840×[email protected]" The tech specs used to mention 4K at 60Hz ?.
I've since switched to a CalDigit TS3 Plus and couldn't be happier!
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.
tl;dr: The cable is well-built and delivers 4K at 60 Hz without issue. And the DisplayPort end even uses the locking mechanism to ensure it's retained better—but it's also a tiny bit longer of a connector than most others, meaning it's not the best fit if your monitor needs to fit in a tight space!
When I upgraded my 2016 MacBook Pro, I decided to also replace my main external display (a 1080p 27" monitor) with a 4K UHD equivalent. Since I work on my computer all day, I find it's important to have as good a display (sharp, good color, etc.) as possible, to prevent eye strain.
4K displays are interesting beasts—there are so many pixels on these displays that even decent older laptops (like my former 2013 MacBook Air) couldn't drive a 4K display in native resolution, even if I had the proper mini DisplayPort cable.