I own two older RePlay units, and have co-workers that own Tivos.

The Replay's price includes the lifetime subscription service, the Tivo's service costs another 200 dollars.

Both units only have one tuner, and as such can only record one thing at a time. I believe MS has a combo
satellite unit/Tivo that can record two things at once, but only from the satellite service. (I may be slightly off but I do know there's some kind of limitation on the two recording thing that isn't advertised.)

The RePlay natively has the 30 second skip button. This is a killer feature that I really, really love. Four hits of that button and you're back to watching your show, no commercials. The next generation (of both, I think) features a total commercial skip feature that is automatic. (They're being sued over this, of course.)

The Tivo is actually a Linux box. You can thus hack it and tweak it to your heart's content. I've seen people run web servers, add ethernet cards, and do all kinds of funky things with it. The RePlay uses an embedded OS (non-linux, though I forget the name), and as such isn't as easily hackable. (Though you may want to check the AVS forums to see if there is anything new, I haven't done that in a while.)

The interesting thing about the Tivo is that it takes the unused space and will record things that it thinks you may like. These recording decisions are based on what you already have scheduled to record. I know my co-workers have been very pleasantly surprised with some of the recordings. And if it nabs something you don't want, you can just delete it (Tivo only uses your unused/reserved space for this kind of recording.)

Also, the Tivo has season passes, where you can tell it "Grab all the Simpsons", then give different time slots higher or lower priority, and you can tell it to either record copies of the same show or not. (The Simpsons is a good example, as many Fox networks will show it 2+ times a day, and then show the new shows Sunday night. You can set it up to grab only the Sunday night ones if you like.)

The RePlay's not quite as smart, and it doesn't have a priority system per se. It does have four different priorities, but those are based on how you schedule the recordings. You cannot tell it "Record Show A and Show B, and if the two conflict, record Show B." It's final decision logic, if the two are set up exactly the same, is to go with the one that sorts first alphabetically.

Both units allow you to crack them open and change the HD out for a larger one and also add a second one, though I think the Tivo's internals are a little nicer for this (it comes with a second rack, the RePlay only comes with the extra space for one). But, be aware that the RePlay has a memory limit which limits you to 150 gigs of space.

Personally, if I were in the market for a new one (which I will be, soon as I pay off the money I'll spend on Patrick's Tuner *grin*), I would wait until the Moxi comes out early next year. The Moxi is a Linux-based multi-media center. It can record FOUR things at once, and also supports general audio/video/pictures/mp3's/etc. It is truly a multi-media center, and includes a base unit for your main stereo/entertainment center, and then has satellite stations which the base unit can broadcast to. Thus, you can record your shows from the main unit and broadcast them to your other TVs later.

I think the Moxi may even have DVD recording capabilities, but I am not quite sure (it's very late at the moment). I also think Panasonic is coming out with a DVD burning PVR as well, but I know nothing of it's tuner capabilities.
(I think the Moxi might also be a digital cable tuner, which would explain why it's advertised as "coming out via your local digital cable providers Winter of 2003".)

I'd suggest digging a little more about the Moxi. Microsoft seems to be already putting out the word about their competitor to the Moxi, but somehow I think the Moxi/Linux product's just going to be better.

- Rick