Wunders of Wunderlist
I’ve been using the Wunderlist app for iPhone and Web and it’s pretty sweet.
The ‘killer’ part of Wunderlist is that I can use it on the Web, which covers both my Mac and my Windows boxes, and on my iPhone. In the past, I’ve found apps such as this to be restrictive as they are bound to the device. With Web plus desktop plus mobile, you can use it in whatever context you need.
If you need a GTD tool or a to-do-list app, I think you should check it out. I’ve never found a tool that works well for me; this seems to do the trick.