Having purchased and used well over 100 Task apps, I have no hesitation declaring Trello as the best. Boards have lists and lists have items and it is as simple as that. You can have as many Boards, Lists And Tasks as you want, and you can easily move them around. Re-prioritize Boards, move Lists to other Boards, move Lists around on a Board, move Items on a List up, down or to other Lists. Color code, assign due dates, add notes - you name, you can do it. And since Trello resides in the cloud, I can get to it (and all my Boards/Lists/Items) from my PC, iPad or iPhone. And did I mention you can insert a checklist on an Item and yes, even move entries on the checklist up or down. Totally cool. Trello has become my everyday go to app.
Twinsgma2 about Trello: organize anything!