That's not the issue (waiting for the download to complete). The issue is that the download never ever completes. The Computer says "Hey, you can watch your show," but then just a few moments have downloaded, and you get a "-50" error.
The published solution for the -50 error is to navigate to the wack place that itunes has decided to store your download (if you can find it) and delete the partial file and try again.
I have "tried again" 5 times now. It's not working.