As for DRM, whether you are going to use it for DVR or any other media viewing is irrelevant cause its in there, and it does directly tie into the video subsystem. It has to.
As for RC's yes they've been out a while, but at some point they have to lock down certain portions and say (for example device vendors) write to this, this is what we're shipping. A lot can change from when they first got a look at it and when redmond locks it. Now if a vendor has a very small product line up and little legacy to support, that might not be as big an issue. When you get into guys like nVidia, ATI and Creative, to name but a few, then it becomes one.
Vista does have rudimentary support, the nvidia drivers they have dont allow my monitor to go to 1440x900, my monitors native resolution. ANd as stable as that driver is my eyes are more important, so I wil stick with these buggy ones directl from nVidia.