May depend on your TV. I've got 30" monitors and full screen they look beautiful. Absolutely HD quality, though there could be an HD difference between your cable box and computer.
In answers to other questions, while I can't say for sure, I believe you get 24 hours of viewing from the time of purchase.
$45 website purchase as opposed to the $60 cable box purchase (at least for me) not sure if the price differs on location.
EDIT: Just checked the website, apparently the PPV purchase gets your '24 hours of unlimited archive viewing'. Which I guess means you get access to their entire library for a day.