right now if you want to copy several files from A to B
you have to select all files you want to copy at once or nautilus will
start to copy more than one file at a time, this makes copying realy slow.

nautilus should not start with the second copy operation but rather put it in a
queue which is only started once the first copy operation is finished. that way
one could start copying large files while one is looking for the other files that
have to be copied and add them, as one finds them, to the queue, which gets
copied as fast as possible, instead of slowing down the disk due to constant 
seek operations.