My number-one wish for a NGS:

Undo!

Take, for example, rm. The hoops we have to jump through when accidentally rm'ing a file are ridiculous [1]. But in most cases (smallish, non-secret files), rm should be trivially undoable. Windows gets this right: By default, files are not deleted, but moved to trash. If there is not enough space in trash, Windows warns you. Or, if you really want to delete a file instead of moving it to trash, you can press SHIFT+DELETE, in which case Windows will also warn you that it can't be undone. (What is missing in Windows is a "nuke" option that overwrites the old bits with random data, for those rare cases where a file must be purged from the system completely.) But in most cases, after deleting a file, you can simply press CTRL+Z to get it back.

It is possible to make rm behave like that in Linux [2], but in a NGS, this should be the default behaviour (in my view), with "delete" for really deleting (unlinking) a file, and "nuke" for completely distroying a file, as seperate commands.

Undo is hard. Most programs are on their third, fourth, or even higher release before getting it right. (Mathematica 10 is stil trying to get there...) But I think we should try harder to solve the undo-problem with respect to file-system interactions, or with respect to system-settings, in Linux.

[1]: http://unix.stackexchange.com/questions/10883/where-do-files...

[2]: http://unix.stackexchange.com/questions/42757/make-rm-move-t...