Smart Lists Rock!!!!! They help me focus on a subset of my tasks. If you use RTM heavily, you have so many tasks that being able to see what you really need to see at a particular moment can be difficult.

It would be very handy to be able to duplicate an existing Smart List. Then it could be customized.

I have a number of Smart Lists which differ from each other in small ways, such as things due strictly today, or today and tomorrow, or today and the next week. Then I have lists with the same criteria except they are limited to only Priority 1 items.

In the web app, at least, there is a drop-down menu next to each Smart List. It contains "Edit Smart List..." and "Remove Smart List..." It seems like it would be very simple to add a new option, "Duplicate Smart List..." The new copy would be the same as the existing one with the addition of the word "Copy" to the list name.

In the iPhone app, this option could be added to the current "Delete Smart List" option at the bottom of the screen where you edit the parameters of a specific Smart List.