Based on the VLC bent in this thread, I may be completely out of school with this suggestion just hear (or read) me out:
But it would seem to me that something based on the XBMC (also the basis for Boxee and other media center software, and it is also cross-platform) plug-in architecture would be a good investment. These would also give a better experience, and avoid the "sittin' at my computer watching RiffTrax" syndrome. Obviously a Windows Media Center integration would widen the market, but you know, one thing at a time.
There are also additional commercial opportunities available:
When a user puts in a DVD or Blu-Ray of a movie (... maybe even fire up the ripped file) that has a Rifftrax available, have the plugin notify them... if you integrate and streamline the purchasing process, you could move a lot more product. Show the catalog of download-able content to give people an opportunity to buy, download and watch them all with their remote. Mindless and Seamless are good. Sand-alone players are acceptable (and definitely better than nothing), but I think that if you are after more market share, this is the money shot.
I love what you guys are doing... keep at it.