Tracking when I workout, notifications (I carry two phones and during the day my personal phone is in my bag most of the time). And just using it as a watch. I hated that most of the "smart watches" out there would either run out of battery in 8 hours, or have the screen off by default (with a wrist action or a button to enable it).

I don't use the sleep tracking at all, hate having a watch on at night, but the step tracker is fairly accurate and useful.

It's one of those things where I initially bought it for the notifications and the (supposed) battery life. And every now and again I'll find some random new cool use.