wyvrn - Chances are the phone company didn't use twisted pair - why pay extra for higher quality cable? Time to get out the old crimper. In addition, 10/100Base-T uses a star topology, not a bus like HPNA.
goog4 - yes HPNA 2.0 cards are backwards compatible. But if you have one 1Mbps device on the network, all devices will run at 1 Mbps, even if two 10Mbps devices are talking to each other. It's part of the protocol spec.
In addition to the netgear, you can get the Panasonic gateway for $99 at compusa. This includes NAT routing functionality (see review over at
www.practicallynetworked.com). You can upgrade the panasonic to wireless later on, but beware their wireless design uses a different spec than most other wireless devices (802.11b).
For comparisons of the SKU to other web sites, the rebate is only good for the 1Mbps version. The last 2 digits of the 10Mbps SKU is 31, while the 1Mbps version is 13. Otherwise this would is a great deal.