I have the older 5000 series which has the Internet Sharing feature and Commerical Skip in tact.
Works great, never had any problems with it. I have the 5040 model (40gb drive) upgraded with a 160gb drive. I believe it is now possible to upgrade the unit with 2 physical hard drives now... 500GB??
This give me about 50 hours of record time at the highest quality.
It is hooked up via 100mbps ethernet. Using DVArchive you can rip shows and stream them off the Replay as well. Basically DVArchive makes your PC look like another Replay unit. You can also use an 802.11 B/G bridge if you want, however I've heard streaming doesn't work very well, even with G's speeds.
One nice feature, if you have two replay units, is the ability to watch a show on one unit, pause it, and continue on the other unit.