As a long time Apple customer (starting with the iphone 3 on AT&T which was horrible) I've held off getting an AW until a few weeks ago. I just got the AW4, and while I like it, I have to admit I'm not sure it was worth the $640 (44mm, aluminum, cellular, apple care). I got the cellular version even though I don't have a cellular plan for it currently, with the hopes that cellular support / capability will improve in the future.
While the AW is good for Notifications, Heart Rate tracking, and to a lesser extent sleep tracking. The Misfit Shine 2 I got for my 7 yr old for $~30 is almost as good save for the display and apps (though it looks like Misfit is going out of business? All their activity trackers are out of stock now). Since I have my phone with me at all times anyway, I kind of wanted an apple watch "just because." And because I work in a laboratory it lets me easily check the time, notifications, meetings, etc. without having to take my gloves off.
That said, the AW4, while aesthetically very nice, still feels like a woefully "underdone" product. I'm glad I waited until now to get one as it seems just barely passable given the cost. Honestly, an on sale AW3 would be just as good for several hundred less (I've seen the 42 sans Cellular on Amazon for as low as $229-259). I've thought about getting one for my older son (he desperately wants one -- to show off) who has a Garmin Vivo Active 3. But I think that when he gets it he'll prefer the Garmin.
I have 511 (yes, 500+) apps on my phone (just upgraded from a 6S to XS Max -- but that's another story of remorse) but just 46 of them support the apple watch which seems shocking given that the AW is like 5 years old. Overall the AW is probably ahead of the Apple TV, but not by much. 6 of these apps I just bought in the AW itunes store!?!
Blink? No
Ecobee? No
Facetime? No
Amazon Music? No
Pandora? No
Alexa? No
Google Assistant? No
Lync / Skype / AT&T Connect? No
the list goes on.
I wanted the AW4 for the EKG functionality. Which is nice, but I didn't realize at the time that you can add this same functionality (using a stand alone Bluetooth enabled sensor) to the AW3 for $100. So you have to ask yourself is it really worth it?
Search for
Alivecor KardiaMobile EKG Monitor
You can also add blood pressure (search for)
Omron 10 Series Wireless Bluetooth
I think the Apple HealthKit is really the star of the show. The AW is really just a gloried remote display / remote control for your iPhone.
So unless you really, really need one of the new AW4 features, save yourself $400 and buy an AW3 onsale at Amazon, skip the apple care, and plan to buy a newer better one in 2 to 3 years.