has no ads, content is free and is made by an Australian non-profit;
has lots of programs targeting different needs: simple meditations, programs designed to help improve sleep, short breathing exercises for when you're in panic, stress relief, concentration...
there's also a 30-day "mental fitness" challenge to keep you hooked;
wellbeing check in and reminders;
offline downloads.
Cons: (so far)
starts feeling repetitive once you use it for a few months but I guess that's normal, exercises are still cool;