That's a very good question. I saw herdfan post it on TCF and thought I would research tomorrow and see if I could get an answer from DIRECTV.
As far as more information, here's a brief recap of what we know.
The first generation HMC will feature 6 tuners, 2 OTA/ATSC and 4 SD/HD Satellite and is due out January 2006 and will support up to 4 SD clients. Clients can be connected via CAT 5 or coax. HMC servers can be connected together to provide more clients. Later versions should support WiFi and HD clients.
No price has been disclosed, but the model looks like a rental offer for $10/mo.
DIRECTV is also working on the next generation HD DVR (MPEG-2/4, due out around the same time.
-Robert
VE Advanced Digital Technology Dealer