Is HD-Tivo worth the price?

I have a HD-DVR that I pay 6 bucks a month for through my cable provider, and although it sometimes does not always record what I set, its pretty cheap. What is the point of buying such and expensive piece of equipment such as the HD-Tivo because at costco its $300, there has to be another reason why people buy them, because it would seem everyone would just pay the 6 bucks a month. Any feedback would be great. Also, if I get an HD-DVD player, will my normal dvds be in HD?