Subly

I've tried a lot of apps over the years, including others in this category - and Subly is hands-down amazing. It's quick and super easy to enter your data, the configurable spaced reminders are genius, and the reports are excellent. Honestly, I don't impress very easily, but with Subly, I am impressed. This is so much more than just a "subscription" app - this is a billing and organization tool that will take a real burden off your shoulders. I can't imagine anyone not finding this incredibly useful, whether they use it for business or personal use. Five stars plus!