I’ve been using Todo.txt for a little while now. I love it for it’s minimalism. Simpletask is a more polished approach to Todo.txt. It has some nice additions like grouping tasks by project and more configurable widget. Simpletask on Play
There is nothing wrong with this app, it just doesn’t have some of the niceties of Simpletask. You should gladly give Gina the $2 for coming up with Todo.txt.
While not what I’d pick for independent task management, Trello is great for collaboration. I use both Simpletask and Trello daily.