The main troubles with Internet and/or Satellite recorded PPV is... in the DirecTV+DVR model they will self destruct after 24 hours after you start viewing and will not have a rewind feature to restart from the beginning.... while not happening today it is reported that it will start happening in April'08.
Dish Network PPV does
NOT self-destruct with a DVR. It's there until you delete it. My issue with HD PPV/OnDemand is that most of the movies are open matte or cropped and not OAR. I don't mind a few black bars in my 2.35, 2.40 and 2.76:1 movies.
Pan and scan/foolscreen is for 4:3 CRT's. That sort of stuff has no place in the HD era.
If cable and satellite companies got their content together and somehow got the studios (other than Warner) to remove that waiting period between when the DVD/Blu-Ray(previously HD DVD, too) goes on the shelf and when the PPV movie is available I believe that would be a bigger draw.
Now, Internet VOD/downloads? Err... no. Most of the solutions are too slow, too cumbersome, too expensive and look worse than Blu-Ray/HD DVD and even sometimes upconverted DVD on screens 50" or larger. Moreover, some of them are actually for purchase. Here's the problem I have with purchased downloads. You can't share them with a friend the way you can with physical media. Moreover, they're attached to whatever device you used because they are pretty much DRM'd beyond all recognition. (This only recently changed with music.)
No one mentioned Blu-Ray's sound upgrades over cable/satellite/Internet. Why? The average consumer doesn't care about sound in the mp3 era.
I can see the rental market getting dinged by PPV/downloads if the studios day and date them with the standard DVD/Blu-Ray. I don't see the purchase market going away just yet especially since Blu-Ray is pretty much in the hands of videophiles (not even close to mass market) that actually care about higher PQ and AQ.