<< Couple of questions for all cable users (basically, everyone but me 🙁 ). >>
If I remember correctly, only 20% of all online-capable households have broadband of some sort. So you're not quite alone. 🙂 (I have cable, by the way.)
I've heard that renting is sometimes a wiser choice, because many people have had their cable modems die on them after a few months. If they're renting you a $100 modem @ $10/month, and it dies in six months, they replace it for free and you end up saving money (assuming that if you bought the same modem that it would die in the same period of time).
It's hard to say though. Generally I don't have components that just up and die on me, and this particular cable modem has been running for a year and a half.
So check out what kind of modem they're renting you, and how much it'd cost retail. If it's some ultra-slick $180 modem and they're charging $10/month, you might want to think about renting if you feel that it could die in 18 months.