Re: "what the hell good is it?"
Example: watching TV. Do you have your iPhone in hand? No. But you have an iWatch on your wrist. No need to look for the remote, just touch the watch to pause what's onscreen. Go to another room, touch the iWatch again, and the playback resumes on that TV. Room getting cold? Use the iWatch to turn up the thermostat.
Example: leaving home. If you forget your iPhone, your iWatch lets you know. When the iWatch leaves, the Apple TV gateway alerts all of your linked devices to go into their "away" settings. TV off, lights off, etc.
The point of an iWatch (in my estimation) is that it is a simple, versatile UI that is always with you and can control what's around you. If you need to run an app, use an iPhone or iPad or whatever. But to quickly control your environment with just a touch, use an iWatch.