A really nice idea. The only limitation that I could find so far is that it won't move a file
in the rare case where there's already a file with the same name in the destination folder.
Of course, it shouldn't be difficult to fix that by adding a number to the name of the new file.

Now what I really like about it is that the script can be edited.
For example I added, after the folder is opened in the Finder:

tell application "Finder" to select every item of added_items

So if that folder contains many files already, I will be able to find the newly added file easily.