I used to have one of the old Replay 3030s... it was great... I was very satisfied (as I'm sure the ebayer that buys it will be). There are some quirks to the Replay UI that could stand some improvement (conflict resolution is the biggest).
Anyway, I just bought a Replay 4540... mainly for the LAN connectivity. WOW
This thing is SO cool. As you may or may not know, the LAN-connected Replays can send and receive shows to other Replay users over the Internet. So if you forgot to tape "Six Feet Under" (or are too cheap to pay for HBO like me), you can find someone who does have it and they can program their replay to send it to you. Granted these shows are big (~500MB for a half-hour), but who cares? You will receive it all eventually and then it's on your replay as if you recorded it yourself.
Going along with that, some genius wrote a java app called DVArchive. You run this on a computer on your LAN and it simulates a replaytv unit. Meaning that it can access your replay over the LAN. You can stream shows off the replay hdd to your computer, or transfer the show entirely over (in MPEG-2 format) for archival. You can schedule the program to move shows off your replay to your computer at specific intervals (like if you want to archive all episodes of something to HDD/DVD etc.). There are tons of uses.
My favorite feature though is Commercial Advance. Replay has always had an edge over Tivo in the fine art of skipping commercials. They have a 30-second skip button (as well as the 6-second Instant Replay button), and after a while you develop a knack for knowing how many button presses of each to get through a whole commercial break.
With the new replays you don't have to (90% of the time). SonicBlue developed an algorithm to detect commercial breaks and it works like a charm. I recorded SNL last night and the replay successfully skipped every commercial break but the last one. Frankly, I am amazed at how well this feature works. When I bought the unit I thought it would be sort of gimmicky, but I stand corrected. If (for some bizarre reason) you actually do want to watch the mindless advertising simply turn off the Commerical Advance feature (the commercials are always recorded... the Commercial Advance feature does its thing during playback only).
To top it all off they improved the conflict resolution abilities in the new models. There are still some things that Tivo does better, but none of them are as important to me as the automatic commercial skipping and LAN connectivity.
The only downside is price. Replay changed their pricing model such that they require a subscription (either recurring or one-time) to stay competitive with Tivo. For absolute n00bs, I would say a Tivo is probably easier to use. But if you have any interest in the geekier aspects of these then I think Replay is your best bet.
l2c