I love my DVR! I have an old square tube TV and simply the basic network channels via Comcast, but I haven't needed any extra box or digital converter. I can't remember offhand how all the wires are hooked up in the back. I don't know if it's Cable > DVR > VCR > TV or if it's Cable > VCR > DVR > TV. We have our old VCR hooked up, too. So, potentially, we can record one channel on the DVR, record a second channel on the VCR, and watch a third channel live.
My inlaws lease a DVR through their cable company. I think they can record up to two shows at once, which is a nice feature, but it only allows them to record in 1/2 hour blocks. I always like to start recording a few minutes early and end a few minutes late. That was especially necessary recording shows like Lost that would often run over a few minutes.
I've been very happy with what we got. It's a Phillips and it's also a DVD player. So we can actually record stuff to the HDD Hard Disk Drive and then burn it to a DVD. It's pretty handy to burn 6 hours of kids shows to one DVD for those long family car trips. :)
With small kids, we got in the habit of recording everything we want to watch for viewing later. It's nice to be able to skip through the commercials anyway. Getting the DVR makes that much simpler. We don't have to worry about being at the right place on the tape or running out of space when we go out of town. We can watch things in any order and simply delete the title when we're done with it. It also remembers your place, so you can stop halfway through one show, switch to another, then simply return to the other one and pick up where you left off.
Ours also lets us edit what we record, so you can take out the commercials before you burn to a DVD.
Takers is right, though; now that I'm used to having one, it would be pretty tough to do without it. How easy it is to get spoiled. :o