I am using IdeaMatrix and ToDo Matrix. I did the trial for about 2 days and recognized what a killer app this is and bought the two. Both are worth every penny. And it's as powerful as you want or as simple as you want. I can't imagine going back to my old PDA task list and until I used ToDo Matrix and IdeaMatrix I couldn't imagine myself saying that. Brilliant apps and nothing comes close. If/when you buy one or both, I'd also recommend reading the Whitepaper.