I LOVE the progress of technology, and I LOVE the idea of a future where we can just use 1 port for all our connectivity needs.
What I DON'T like is Apple's approach. This isn't like removing something as large as a CD drive from a mobile computer or replacing a jumble of proprietary ports with one connection. This is replacing all physical connectivity with a single port without any sort of transition period. Had they added USB-C to the rest of the Mac line when they introduced it 2 or so years ago, that would be understandable: give people a chance to have some familiarity with the new standard before fully adopting it. They're telling me, "here's this new computer, but you can't connect ANYTHING you have on your current computer without buying all these dongles first, just have some courage."
Compounding this is Apple's track record with promoting new ports. Sure, USB and CDs were a success, but multiple versions of Thunderbolt and Firewire completely floundered all while Apple stubbornly and repeatedly refused to adopt micro-USB, mini-VGA, and HDMI even when the rest of the entire tech industry had standardized them. We have every reason to be at the very least skeptical that USB-C will catch on.