If you want to refine you queries in Google Video without fiddling with special operators, you can use the advanced search. You have less features than for Google Search and they are slightly different. You can restrict the search to free videos, to certain genres, there are options for the duration of the video and the number of results.
All of these options were previously available, but you had to use undocumented operators like genre or is:free. I still don't understand why you can't sort the results by the number of views, or the number of comments and why you can't combine two or more labels in a query.