Please do not delete the original wma files by default. While this is a great option to have, it should be something the user has to do on purpose.
I started converting a directory, but didn't like the 128bit rate it choose so I started hitting ctrl-c to kill it. Low and behold! It was deleting the originals!
I suggest having a -d/--delete-original flag or something.
Otherwise, thanks for the script.