It's probably best to get this out of the way first: I am pretty sure I want one.
I'm skeptical, even still, of the orthodox smartwatch concept. If all that this thing can do is mirror some smartphone features but with the whole raft of limitations that comes with the tiny little form factor then it has pretty limited value. There were two clear approaches to this problem. You could eschew much of the software interface and focus on other functionality that is enabled by the device's use (such as the heartbeat monitor). Alternatively you could start with the smartphone-extension functionality but go somewhat beyond it. Either way this watch thing has to justify it's existence beyond the features of your smartphone.
Some of the communication stuff (tapping and sketching) feels to me more like a technical demo than a useful feature. These things are kinda cool from the perspective that there might not be anything directly comparable but I think that most people will tire of the novelty and they'll fall out of use. They don't seem to convey the same quality of information as, say, an emoji the likes of which most of us use to convey emotional cues alongside more sterile text on an almost by-message basis. Navigation by haptic feedback again is really neat, but I don't think it will justify the device. The health stuff does seem pretty meaningful to me. It's simple, I can imagine the number and variety of sensors increasing with future generations, but I think it has some value. I'm interested in this, not interested enough to prompt me to buy a Nike Fuel Band or a Jawbone or some other fitness tracker but coupled with the watch's other features it is attractive.
If you remember the original iPhone, it did very little. There was no App Store (Apple initially seemed to be headed in the direction of using the internet and web apps to extend functionality). While it did more than the Windows and Blackberry smartphones that came before it (largely thanks to having a true web browser). The Apple Watch has an advantage here in that it's building on a mature software platform. There is an API which will enable app development from the start, and while Apple have covered all the obvious things I am interested to see what developers will do with this. I can see a lot of potential with geofencing and push notifications, for example. The very best software for iOS has always been put out by third party developers.
One of the things I've noticed with iOS 8 and Yosemite's continuity features is that my phone stays in my pocket a lot more, particularly when I'm at home and usually have another screen in front of me. The watch supports these features, so I'm curious if it will have an impact.
Even after all this is said you can't dismiss the appeal of something new and shiny and fun. People have asked whether or not I feel it's overpriced. I don't think it is. There is an XBox 360 sat under our TV that's only ever been used a dozen times that was significantly more expensive even before adding the expense of the games and it is debatably less useful. So no, I don't really think it's overpriced, and absolutely not if it realises some of it's potential. At the end of the day I'm old enough and young enough to admit the appeal of a new toy and can justify it on that basis alone.