[Mojombo]

I use both.

Things I use only for very simple, immediate lists. I barely use any of the fancy features. Things opens really fast, and its UI is actually better than any of the simpler apps for quickly adding an item.

OF is for real planning. It opens way too slowly to be useful for a quick on-the-go list. The feature set is fantastic for big-picture thinking, though. It's no good for planning an afternoon, but it's perfect for organizing a life.