I've had mine for a few months. Frankly, I think it is currently unimpressive in terms of functionality. It really needs better software (with and apps). Knowing what I do now, I'd wait until the new watchOS comes out this fall and see how much it improves before I'd spend the money.
I've found the nice features to be:
Seeing text messages while driving. A quick glance tells you who and what (and if a reply is critical).
Answering the phone when your phone is not handy - and then transferring to the phone when you get it.
Stock quotes with a finger flick.
It's a watch.
Not so great:
Anything related to actually using it as a sport device. The HRM is accurate (compared to my chest straps) but none of the fitness apps I like use it (Strava, Digifit, TrainerRoad), you still need a chest strap. This should improve in the fall.
You can't control how long it stays 'on' before going black again. And it's too short for my taste. (If it even comes on at the first attempt.)
Sunrise/Sunset almost never works.