Xbox360 owner here too so here are my 2 cents worth.
I have everything setup to stream almost everything I want to my xbox and I also own a Pinnacle Showcenter 200. JR would be hardpressed making me pay extra, but it would happen if there was support for external subtitles (.SRT files). Another option would be realtime transcoding of HD material in the video's native resolution
.
Maybe JR could consider making it an addon/plugin, so only those who want it pay for it?
But I also like to point out that there is a usability issue with Media Connect feature for the Xbox. It does not support subfolders and consequently all your videos will be displayed in a more or less random order in one big list. At one point I had a couple of hundred small videos and browsing for the right file becomes undoable. This is NOT the way I use the media features of my Xbox, I use Windows Media Center (Vista).
What would be much better IMO is if (features of) JRMC12 would be available as a plugin in (Vista) MediaCenter extender for the Xbox360. No idea what it would take though to create such a thing but it is possible because others have already done it.
I would also think that once something like that exists that quite a few xbox360 owners without MC12 would consider MC12 because the current options are limited and difficult to implement.