This is a To-Do app that's slowly getting there. Overall, the UI has improved by being feature rich while maintaining simplicity. It still lacks in some areas such as robust custom repeats, contact linking for email or phone calls, and acceptable speed performance. I'd give it a B- to C+ but it has a single feature that's missing from my previous favorite, 2Do, and that's Exchange-based accounts.
I'd say in a year or two, this could be the best To-Do application out there, especially with the iOS versions. In fact, I'd try the iOS apps first before making the investment in the Mac version...for this app development, that'd be the proper horse before the cart.