Your app reminded me I wanted to watch Khan's videos on IPOs, so I type in: IPO ... about half way down the list of ~50 results are the videos I wanted to watch (An IPO, More on IPOs).. I actually had to do a Ctrl-F to find them in the result list.
I use quicksilver.js to match items. I probably need to increase the score threshold to ensure more accurate results.
Currently, it only "searches" the title of the video and the playlist name. If I had transcripts of the videos (they may exist somewhere?) then it could be WAY more relevant.
Some videos show up twice because the same video exists in two different playlists. I'll fix it.