Yes, it does appear a bit thick from certain angles, but if you consider all that is crammed into that tiny enclosure,
I for one am actually amazed.
As a stand-alone device (with even more tech built into it), as well as yielding longer battery life (another oft-desired thing), would make it even bulkier no doubt.
I think for now, the premise of this device is near-perfect: a fashionable and customizable, wrist-worn companion device to a smartphone (which virtually everyone has these days), for almost hands-free operation of many ordinary and repetitive functions, while keeping the larger, and more drop and theft-prone device, safely tucked away most of the time.
Once a multitude of specifically tailored Apps start making an appearance, the AppleWatch will become an even more amazing device, that soon we'll be hard pressed to do without. If there's any doubt about that, all we have to do is think back to the days of 'dumb phones', and how the iPhone completely changed the way we use technology and communicate.
To come back to those size objections many people seem to have, it's a no-brainer that with the unstoppable pace of miniaturization, and hopefully revolutionary battery technology, all necessary technology will eventually be contained in the wrist-worn AppleWatch, making it a stand-alone device.
We're just not there yet.