I have a simple use case. I want o copy some music. I have an 8Gb pen drive and my Music folder where each album is a directory inside the artist name directory. I select some artists. I select a couple of albums and dragn'drop them. Select some more, and copy again. The file manager almost freezes.
The problem is that Ubuntu tries to copy them simultaneously, instead of just queueing them. This parallel writing is extremely slow.
Yes, I could ctrl select every one and do just one dragn'drop action, but my experience is that I'd make a wrong click and undo all my selection.
I didn't think that it would be a problem in 2013.
I'm sure this a general Linux/Unix behavior since the same thing will happen on a Mac. (Pretty sure it happens with Windows as well.) Every file copy operation is independent and added to the I/O queue and the OS will attempt to execute them simultaneously rather than sequentially even if the destination is the same. Going to a USB device can exacerbate the situation even further since the data throughput is considerably slower than the hard drive; then add the overhead of maintaining the directory information on the USB drive with multiple I/O executions running and it just bogs.
Stick with the Control-click route: if you make a mistake, Control-click the mis-selected file again and it will de-select it.