Based on my experience with my Samsung G2:
The utility of the smartwatch comes in when you can synchronize your data on the two devices; and there are a couple of "killer apps" when it comes to smartwatches:
Phone/messaging is the obvious one, and the use-case for READING (not responding to) messages is pretty useful, especially if you're receiving a lot of status from various people. Phone-calls are also pretty useful, but a tad awkward; audio is not private (you are on "speakerphone"), and I can say that the output of the Samsung is weak-enough that it's not all that useful for phone calls.
Time is another one, and that's a no-brainer. I don't have to re-set my watch 2 times a year for daylight savings. Tracking my location and re-setting for time-zones is very handy, for people who travel a lot. Don't underestimate that one. Samsung has not yet really fucked this up, but it relies on having your phone with you, and powered-on.
Weather used to be VERY useful. I don't know what Samsung did, but they changed their phone-based Weather widget, and now it does not run at all, so it wn't send time to the watch, the watch weather client doesn't know what to do - it's sad. It has nobody to talk to. It displays the weather data from 9 months ago, when it stopped synchronizing. There are MANY online discussions where users are mentioning this problem, and Samsung has completely ignored it. Obviously, they wanted to ship a product, make their $ from the outrageous price tag, and then abandon it so that it becomes obsolete and ceases functioning after ONLY ONE YEAR.
Health is another killer app; and Samsung initially had it down pretty good. When I first got my gear, it integrated fairly well with my Samsung sHealth app on my phone. And again, Samsung updated their mediocre-but-functional s-health app, and now, it no longer uses the heartrate monitor on the watch. The app tracks your location, but only via PHONE instrumentation (ie. you need to stuff your phone into your nylon running shorts to track your runs). The phone and watch pedometers fight for dominance. Neither are accurate. Neither are consistent in their accuracy. When you track your activity with s-health, you never know if it's using the watch pedometer, or the phone pedometer, and you don't really care, because both readings are garbage. It would be nice if we still got the ongoing heartrate data from the watch. But that doesn't work anymore.
Again: many many many people have complained about the changes to the s-health software on line, and Samsung has completely abandoned all forms of support for this product. If you have an S7, I think they care. One assumes that in 6 months, if you don't have an S8, you will probably want to through your S7 into the garbage.
So why am I talking about the Samsung crappiness in an Apple thread?
Apple also has a LONG and well-deserved reputation of shipping SHITTY software updates that degrade functionality of equipment, and try to encourage you to buy new hardware, at a rapid pace, long before the hardware has ceased functioning. I don't know if this is the case for the Apple watch. I don't have one. I also don't have an iPhone, but I've seen this happen with their iPads, and with iTunes over several generations of laptops and desktops. (Does Apple even make a desktop anymore? lol - of course, I know they do - but let's face it. Not really.)
I hope I have saved at least one reader from wasting their hard-earned money on this junk.
I have not heard the same complaints from people buying health monitors and watches in the Android ecosystem. But I honestly don't know anyone who has one of those. Samsung and Apple have really sucked the chrome off the trailer hitch here.