Lol. People who are talking about USB-C just being standard USB are missing the point.
Yes, the new connector is the same USB protocol as USB 3.0 (now renamed USB 3.1 Generation 1). However, the USB-C cable includes alternate mode. In other words, that USB-C cable can carry other signals in addition to the USB data stream. So now, instead of just being a single data port, it's now your power, data, and also DisplayPort connector all at the same time. It does far more than just 'change the shape of the port'. So hypothetically, say Microsoft replaced the SurfaceConnect and miniDisplayPort with USB-C while leaving the third as USB-A? You'd then have enough flexibility for two monitors connected directly to the device... or maybe transferring between two flash drives without needing a hub... or if they took the Chromebook style approach? Being able to charge the device from either side without worrying about where the cable is. Or how about just the ability to use the same 'dock' for your Lumia 950 and your PC for when you need to quickly attach to a larger screen in a pinch?
And on top of that, Thunderbolt 3 uses a type-C connector as well. Which would mean that from one universal port you could also attach an external GPU if Microsoft decided to use Intel's Alpine Ridge.
But since changing the size of the port and all was mentioned, I cannot believe anyone is spinning that as a bad thing. First of all, it's about the same size as microUSB (only a few millimeters larger), so it's not really a 'medium sized port'. And secondly, yes, when the size of a port is limiting the size of devices (SP4 has to be a certain thickness in order to keep the USB-A port), then it's time for something smaller to become standard.
And personally? After all the issues I've had with my Pro 2 charger cord (I've had three replacements - the stress relief right before the magnetic connector is not good enough and it's very common for the connection to be lost there), I'm done with proprietary chargers.
Honestly, I realize that Microsoft promised compatibility with the existing Surface Dock for Pro 4. But for the Pro 4 they could have easily replaced the miniDisplayPort with a USB-C port and came out on top (I mean, everyone uses adapters from that connector already).
And for the Book, they were not beholden to any previous promises. The Book and the new Surface Dock should definitely have been using USB-C (preferably Thunderbolt 3). Leave the legacy Pro 3 dock available for SP3 and SP4, and then when SP5 comes out and supports the connector, then the new Dock would be compatible. Instead, they've released a brand new dock which is really just a placeholder for now until they finally decide to implement new technologies.