The subscription does go with the machine, so if you buy one with a lifetime subscription, you won't have to pay the monthly fees. But I don't think the subscription can be transferred from one unit to another, so if your unit breaks, you have to buy a new machine and subscription.
If you get one of the original "Series 1" units, you can use it as a digital VCR without paying any subscription. You don't get any of the neat features (show listings, season pass), so you just record by time (like a regular VCR). I bought a Series 1 Tivo for $100 a while back and use it this way (I am too cheap to buy the subscription). Even without the subscription, it's still much better than a VCR (IMO).
John