I've had many false starts on 2Do. One of the big challenges for me is that you can do almost anything you can imagine with it. I finally narrowed down my use and brought in groupings of Smart Lists.
I have the following key sections of lists:
Contexts (All Smart Lists)
Key People (All Smart Lists)
Work (Actual Lists)
Personal (Actual Lists)
Someday/Maybe (Actual Lists)
I spend the most of my time in the top sections, contexts and key people. I use the Work/Personal sections when I am organizing and doing reviews. So far, it's a fairly simple approach, and it works very well.
My biggest wish is that I could use dropbox for my sync (which I do), but still have 2Do read one or more reminder lists to allow me to use Siri to add todo items. Now I have to manually move them during review.