I've speculated before that CableCARD was going to reduce the value of WMC, today Chris Lainer posted some confirmation that CableCARD content will not play nice with others.

"just as with current CGMS-A protected content it [CableCARD content] can only be played back on the Media Center PC it was recorded on (inside of Media Center only, not in Windows Media Player) or a Media Center Extender."

...

"Another bit that you can not do with CableCARD recordings is convert them to go on portable devices (Zune, Portable Media Center’s, iPod’s, etc)."

I was disappointed when Microsoft announced that CableCARD was going to be an OEM only feature, but this is too much.  Removing the ability to do useful things to the content on your PC destroys the value of having it there in the first place; making the PC a "closed box", with none of the benefits of having a traditional "closed box" in your A/V stack.  If I "needed" CableCARD, I seriously consider a TIVO. 

I wonder how CableCARD users will react when they discover that they cannot archive, burn, place shift, edit, their dvr-ms content.