Product North Star is always a leading metric. <WIP> talk about key infleuncers etc and goals. Gathering a baseline and then setting metric goals.
Happiness - How happy is your user?
Engagement - How engaged is your user in the short term?
Adoption - How many interested users have actually tried your product?
Retention - How many users do you retian long term?
Task Success - How successful are you at allowing users to perform the most valuable task?