cursor for DND->copy and DND->move should differ more

Binary package hint: ubuntu-artwork

When you drag a file, it's cursor changes to indicate that wither the file will be copied or moved when it is dropped. Right now, the two are barely distinguishable.

This causes a bit of a usability problem because the default drag'n'drop action differs depending on if you drop the file on the same or a different file system.

Here are two suggestions:
for Move, have the cursor change to include an icon representing a document with a curved arrow point from nothing to the document
for Copy, have two slightly overlapping documents

I'm attaching a *rough* (I think you'll agree that its rough) sketch of what I'm trying to describe.