For me, the big mental block is that I can't think of much I want to do from my watch. A readable screen is obviously nice. So is advanced battery life. But, if I'm going to be dipping into health tracking, it seems Garmin is the baseline there.
The UX flow is one that has me somewhat intrigued. How often are you interacting with the device? And for what reasons?
Bluetooth headphones often have media controls but in my experience they tend to be hard to use on wireless earbuds due to their size. Using my Pebble is much easier. No other smartwatch I've used has done this quite as well.
The only experience that came close were hybrid smartwatches (analog, but with vibrations, 3 programmable buttons and the pointers could move to indicate apps). Longer battery life, but very closed off (can't sync alarms from external sources) and the phone bridge stopped working after some time.
Snoozing alarms and music controls without even looking at the watch (e.g. while in bed, or while walking/snowboarding/etc.) were really neat.
And it kinda begs a question of how much should one want from a device. What is 'enough' so that one doesn't get emotionally attached to it being so expensive it alters behavior with it?
I lost my pebble se after jogging one day, and haven't purchased another one yet (many were too heavy, big, or feature-laden at a much higher price). I sold my original pebble to a bus driver who happened to already have one and presumably just liked having a cheap simple smartwatch for handling notifications and alarms.