I'm curious, what is it useful for? I've been thinking of getting one since it came out, but can't really imagine what I'd use it for after the coolness of the new gadget wears off.
My recommendation would be to try it. If you find it isn't useful you can return it, but my bet is that after 2 weeks you'll find it indispensable.
It's basically a take-a-note app. You talk to the watch, it records and transcribes your message, storing it in an application that's similar to an email client. At the end of my day I would open my inbox and process my notes.
I've also been getting into time tracking and I think there are some apps for starting and stopping timers from the watch.
https://youtu.be/SzZjAMOnPtk?t=240
Shows the watch app starting in about a second or two.
Meetings (Google Calendar). I go to a lot of them.