I'm honestly not that worked up about this having only one port on it. It's an ultra-ultralight that is intended to be used disconnected all day, and Apple will already sell you an outboard connector with a video port, a USB Type-A port, and another USB-C port on it, so you can plug in a hub, external disk, whatever, plus a screen, plus more USB-C stuff or the power adapter. Okay, it requires a dongle. Tragedy--most of the things I hook to my port-covered MBP already require dongles, and the type-A port gives you connectivity for whatever in addition to more type-C stuff.
It will be interesting to see if Apple goes type-C on phones and iPads; it looks a little fatter than the tiny Lightning port, so might not work, but it's at least possible.
My beef with the thing is that it's not Magsafe. The auto-disconnecting power connector is the single best invention in the history of the laptop. I cannot even count the number of times my 3 MBPs have been saved from either getting yanked off a table or couch, or having the port snapped off due to clumsy handling, accidents, wife-not-paying-attention, etc. Anything that's not that is simply a no-go--it's too dangerous, and would unquestionably get broken eventually in my house.
Now, I use my MBP on the couch plugged in a lot of the time, so that edge use case may explain why this will work. Like an iPad, it's only intended to be used when not wired, and has enough power to do so for a full day of use. It will only be "tethered" when charging at night.
And admittedly, if you're going to use it plugged in and sitting on a table most of the time, it's kind of silly to get an ultralight like this--you might as well get something a bit thicker and faster.
Point being, while it seems like a step backward, I'm not the target audience. Just because it doesn't necessarily work for me doesn't inherently make it a bad idea. (Which is the mistake a tremendous number of tech users seem to make--"because it's not what I, personally, want, it's stupid." I don't call forklifts stupid just because I don't personally need one at home, nor do I consider ultra-mini cars stupid just because they don't suit my family's needs. I'm just not the target market. I don't use an iPad, either, but I think they're fantastic computers, and some relatives use them happily as a primary computer.)