That's awesome that they are actually shipping now @Erwin. Are you using the miniDP video out? What are you driving off it if so? I wanted one as it was my last hope of being able to drive a 30-inch (Dual Link DVI) monitor off my new MacBook Pro as I simply couldn't get USB-C alternate mode Display Port out to work, even with a USB-C to mDP then the Apple active mDP to Dual Link DVI.
The USB-C alternate mode display port has been incredibly flakey for me with non-Apple docks too. Only Apple's adapter seems to work, which tells me there's something proprietary about it.
The video out ports on your dock are Thunderbolt alternate mode which I'm guessing is more reliable than the USB-C alternate mode (so confusing that Thunderbolt and USB-C both have alternate modes which are display ports, albeit different versions!!).
I have ended up giving up and just keeping my Mac Pro for when I'm at home, and the MacBook 15-inch is just an expensive portable now. Was hoping to replace my Mac Pro with one computer, but the MacBook is just too much of a compromise on the video out front for me (I run 3+ screens on my desk). Maybe NVIDIA eGPU support will come one day....
For now, the MacBook Pro is for sale in the trading forum as I don't need that sort of power in my 'on the road' Mac.