I remember when Things 1 was released and how much I loved it at the time. Unfortunately it quickly looked dated, especially by version 2 where the UI felt ancient. Version 3 looks quite modern and streamlined and more enjoyable than the current just in the space, ToDoist. However where ToDoist shines is how it integrates with nearly everything. Things appears to lack all of those integrations and doesn't even have quick entry intelligence like Reminders, Fantastical, Google Calendar, iCal, etc where you can say "Take out trash tomorrow at 8pm" and have it automatically parse the date and time. Things does not appear to do that sadly. Though the biggest issue with any reminder app is the apple limitation that makes it so you can't set a third party reminder app for Siri use. And 9/10 times its easier to do a quick siri reminder, than open up an app. Things 3 can integrated with a single iCloud reminder list, but with a major limitation, in that it can't import any reminders with locations. So everytime you say, remind me to do x when i get home, or when I leave work, etc will not be imported.
Reminders has seen little to no love in years, like Mail and Calendar as third party apps have blossomed but held back but lack of native integrations. Let's hope next month Apple announces either major updates to it's core apps to catch up with competitors or allows users to set third party apps as default.
In the meantime time I think this app may be DOA which is sad since it looks great but but a year or two late to the game.