Offline first, native first, seamless sync, efficient UX. I've been using it for many, many years. If I'm not mistaken Things is the first app to introduce the dynamic 'today' list, which many have copied. v3.0 adds native reminders support as well. Calendar is integrated with separation (as calendar events are _not_ TODO items). It's stitched natively to every platform and every detail and pixel has been handled with care.