i just installed Papyrus, and i see that you can edit tasks. its a great app. and this is the rest of the info:
Papyrus turns your Smartphone into a powerful time management system. Papyrus offers innovative and compelling tools to manage and keep track of your schedule, plus advanced views, category coloring, and icons far beyond the ability of the default Smartphone Calendar and Tasks programs. What's more, Papyrus is highly customizable, so it works the way you work while keeping the intuitive and user-friendly interface you expect of your Smartphone.
here is the link:
http://www.sbsh.net/products/papyrus/