It requires an iPhone so you're wrong about the "data plan": long range communications is performed through BT and WiFi via the iPhone and out LTE from there; hence no LTE chip to suck power off the small watch power storage.. Comes in multiple sizes: so you're wrong about "annoyingly large" And thus your credibility for judging the UI? Yeah, not much.
passcode enabling, just like making an iTunes store purchase on an iPhone without TouchID. With my 5s I get offered a choice: TouchID authorization or passcode entry. With a 5 or 5c I expect they'll just be passcode entry. Same as how I used to make iTunes purchase authorizations on my 5.
They listed compatible iPhones that do not have iTouch. On those I expect a passcode authorization will be required similar to when making an iTunes purchase. The holidays would have been nice for the watch (I'd have bought one at least), but a new product's release can be tricky and with the perfection demand placed on Apple such a release would have probably strained the system.
And oddly I'd have expected the case material to be swapped, Aluminum for the "vanilla" and stainless for the "sport", maybe just having been trained too think sport with stainless for all the years dive watches have been made of that material. The easily interchangeable band design is a nice touch.