Sometimes the results you get from a search engine aren't that great (even from Google, these days), and you want a little extra and you want more relevant results. That's where Search Plus comes in.
So, pound on it. Search Plus for Video is in Beta and the way we created it we can make a bunch of changes to the UI/UE via the server-side, so new features and changes/fixes will be introduced much like a web page. It's our first entry into the Firefox/IE Add-on space.
What does is it do exactly? It's very simple. Search Plus is multiple searches in one. Doing your normal search on Google, Yahoo!, MSN, or Ask we'll also query video providers (starting with YouTube) and we'll present the results if there's a relevant match. We're playing around with the UI, location of the results, and other features and doing our best to make the results even more relevant.
Video results are becoming much more relevant, i.e. when you search for "irreplaceable" you probably want to see Beyonce's music video or if you're looking for "NASA voyager" why not see related videos to it versus just reading about it. Anyway, send feedback.