It would be useful to have a progress bar display when moving a file.
At least on OS X, haven't checked Linux, when I move a file it looks like Transmission just locks up and hangs for about 5 minutes (I'm usually moving 4-6GB files), I know that's not the case from experence, but the first few times I really thought it had just choked and hung. I could live with the non-responsiveness if I at least I knew something was going on, but there is no visual indication anything is going on, let alone that a file is being copy/moved.