An end script script would be useful when using for eachs-it would basically end the script.

What about this? Is this planned?

I believe this is "on the todo list", though I don't know what priority it is. I have heard mention of it before. (If you're used to other languages, you might know it better as a "break" statement.)

Here is one logged issue. Perhaps you can vote for it and/or add a personal comment!

http://quest.codeplex.com/workitem/1254

Here's another (which is slated for Quest 5.5):

http://quest.codeplex.com/workitem/1060