I've played with a few DVD recorders such as the Sony RDR-GX300.  If you’re considering a DVD recorder addition to your HT setup be prepared to spend some serious RTFM time.  That is you’ll need to dust off the owners manual read, read and read some more.  I found the controls to be very unintuitive, perhaps the next gen DVD Rs will improve but the DVD recorders available last year seemed about as user friendly as a bottle of cod liver oil.
When connecting the DVD recorder to your system there are as many configurations as purposes for your recorder. 

A popular option (and who can blame you) is recording all those VHS tapes.  It’s best not to use the receiver to pass the video signal through for recording from VHS.  Make a direct audio-video connection from the VCR (out) to the DVD recorder's input, use S-Video instead of the yellow RCA video connector if available.  Using a direct connect will give you a better quality recording all around and the S-video gives superior picture to the composite RCA connection.  Be sure and match the recording time on the DVD-R to that of the VHS tape you’re using for best results.  Obviously, like in the VHS realm you have 2, 4, 6 hour settings.  The less record time you get out of your DVD-R the better the quality.  When setting up your kit that now does a bunch of jobs, recording shows to DVD, and VHS tapes to DVD... you're the engineer with all this gear to get operating.  It's important to remember the first rule of engineering: KISS.  Keep It Simple, Stupid.

The receiver as a "pass through" is handy for switching between devices with one remote control from the couch.  This is great for your regular playback devices IE DVD player.  But for special jobs like recording tapes to DVD you probably want to bypass it.  If your receiver has a DVD in/out that includes S-video and composite (the yellow RCA cable) remember not to mix them up.  If you're using an S-video on the DVD-1 input on the receiver, you must also use the S-video output to the TV (unless the receiver performs the relatively advanced job of conversion) or you'll get no signal at all.

DVDRs with HDD

Many people believe that for editing purposes it’s best to have a DVD-Recorder that includes a Hard Drive built in that records for you so you can commit to disc only portions you want.  This means you can edit our commercials and your DVD Recorder doubles as a PVR.  This isn't necessarily true on DVD-Rs that are DVD-RW compatible.  Many have a list of great editing features.  The Sony RDR-GX300 has a feature that allowed me to place an A mark then a B mark (A-B erase) at any point of the recording (as long as it was a DVD-RW) and then I could eliminate from the entire recording anything between point A and point B (IE commercials).  A great feature, and easily mastered.  Carefully consider the significantly more expensive DVD-R’s with a built in HDD (Hard Disc Drive for recording).  They’re going to tack at least an extra $100 to the purchase price, usually much more.  The HDD set top box such as TiVo or the many satellite and digital cable boxes out there that come standard with PVR are a handy way to watch TV, the ability to pause at any time or rewind is very handy especially if you have a baby in the house.  

When you think about what the PVR adds to your viewing experience I find that I would much rather have it part of my cable box/satellite box and NOT the DVD-Recorder.  The PVR is a great idea; stopping or pausing anytime you watch is very cool.  Having a little baby around the house made it particularly valuable.  I’m leery of keeping your DVD-R ‘on’ to use its HDD while viewing a hockey game.  I don't like to have extemporaneous units on and running while viewing (IE I have no intention of recording a hockey or basketball game, but I want the pause rewind features the PVR offers). 

The second hesitation I have for the PVR/DVD-R combo is that the signal path of everything I watch has to go through yet another box.  The audio from the digital cable box has to be diverted to the dedicated PVR/DVD-R box then to the receiver to "record while watch".  Now, using a digital cable terminal/PVR combo is the cat's ass!  I can watch/record at will and have the DVD-R (if I still had it) off and only switch it on if I recorded (or even just watched) something I wanted to commit to DVD.

Appologies to any regular readers out there.  I am again going away on vacation and will be sent more than a few days.  But when I come back I'll have lots to say.