Update 5/3/2007: It turns out you can in fact share recorded tv seamlessly on Windows Vista Home Premium. It took me a while to figure it out, and it's still a much bigger pain in the ass than it should be (thanks again, MSFT product planning), but I finally found the right registry entry.
One of the coolest features of Windows Media Center is the ability to share recorded tv to different computers (and therefore TVs, if you're using HTPCs). By sharing recorded tv, you can record something on one htpc and it will show up on every other machine on your network.
Out of the box, Media Center supports doing this through the shared videos interface. But with a couple of simple tweaks, including one using the group policy editor (gpedit.msc), you can get the tv shows to show up in the tv section of the Media Center interface. It's totally seamless sharing. Your whole house becomes a networked DVR.
It turns out that you cannot do this with Vista Home Premium because the geniuses at Microsoft have removed gpedit.msc from the Vista Home Premium sku. I don't recall ever reading that gpedit.msc was not going to be in Home Premium, but yet they stripped it out of the product anyway. And now, as a result, I cannot make the computer policy changes to allow the sharing of recorded tv. I've tried changing the settings via the registry to no avail.
Hopefully, I'll discover some work around to this vexing problem. In the meantime, I'll just hope that Apple comes out with a good alternative to MSFT for the htpc community. And I'll bet that they include it in every single edition of OS X.
© Jed Lewison