I found a bug that allows me to download an Unbox vid to several tivoes.
After clicking the download button on the downloads page with the list of your unbox videos, you get a thumbnail page with a drop down box to choose the device and click another download button.
After doing that, a confirm page comes up (for me in a new tab) which I close. I am left with the prior thumbnail page that still has the drop down box. I can then choose another device to download to and click download…
… repeat as many times as you like. I have a vid on 4 tivoes right now.
The downloads to each TiVo happen one at a time, and not necessarily in the order you requested.