First of, this site is really great. I do not know whatever happened to videos from MSDN, but channel 9 seems to be just as good and even better.
I do have some problems with the videos though.
1) Names. Could you perhaps give each download a meaningful name? Like "conference"-"topic"-"presenter". Something like that. Maybe quality in the end - I do not know whether you need that. (Reason: I do not like online streaming, I typically download for later watching.)
2) Quality. Some still have bad audio - I really wonder about that. Sometimes the voice sounds like metal. I know someone could do better there. In some recent videos, video quality has been bad, too.
3) Quality again (this time encoding). I am really surprised about how inconsistent the encoding is. With aspconf I was surprised to find very high quality, low size wmv files after downloading everything as high quality mp4. (From what I had seen before, mp4 was superior in quality and size regarding your offers.) Maybe you could introduce a category for us Windows (yeah!) users who want to have a small download with the highest quality. I do not care about container format, but a consistent link saying "greatest encoding for PC" would be great. You can make awesome quality videos now (h264/aac) with something like 300MB per hour. If it is a movie. If it is just stills (showing a desktop), it should be less than 100MB per hour for great quality. If you invest a little extra upfront in encoding, you would save a lot of confusion on the side of your users and also quite a bit of bandwidth.
Still, I greatly love your site, especially now that all the conferences that are around the globe come (at least partially) do my home/office.