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.

Of course, isn't the price of the Replay unit much higher than the initial tivo cost? The way you worded that particular point was a tad biased. Not to mention that Tivo gives you the option of a monthly subscription. So in the end they're about matched in price except that Tivo is a little more flexible.

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.)

Well, I believe the more popular unit was a Sony DirecTivo unit. My parents have this and I must say that it's a nice feature to have, and amazingly, when I got home and programed a few recordings, we still had conflicts! Yup, we had three shows we wanted to watch at the same time!