For most people, PVR's totally change the way they watch tv. It's one of those innovations that once you have it, you wonder how you ever lived without it.
Regarding HDTV, I think the 2 key content streams that benefit the most is sports, and the movie channels. It's not like Jay Leno is funnier, nor CSI more pompous in HDTV, but hockey or football in HD is stupendous, especially on a big-ass* display. And movies that are well rendered to HD from film are a joy to behold.
*big-ass is industry insider tech jargon. It means "large"