Ok so if you don't have a ustream account and you want to download the video you are watching, in most cases I believe that you can mouse over the video and select "Download this video" when it appears at the top right hand corner of the video.
If you do have an account just follow the screen shots and it will take you to download the .FLV file. That's the best I have to help unless Anonymous would like to jump in and show us how it's done!
I'm exploring replay media catchers and url sniffers for other options. Will update when I know more. Thanks for supporting the blog!