for starters!
Sorry for the long post... tried to go through things in parts tho for easier reading!
stevie, most, if not all DVD Recorders record on both DVD-R & DVD-RAM (or DVD-RW or DVD+RW depending on the manufacturers format)
so you either record a film to keep for all time on a DVD-R and record Corrie & your latest footy match on a DVD-RAM that can be formatted and re-used over & over again like a video... although with rewritable DVD, they don't get damaged and 'wobbly' over time like your not-so-trusty video tapes but instead you get that perfect recording every time...
As for the expense, yep the branded media is expensive (I'm using Panasonic £5/DVD-R at the moment and around £15 for a one-off DVD-RAM) - but with the newer generation of DVD Recorders they are more flexible and cheapo media can be used if you are on a budget - a cheapo unbranded DVD-R can be less than a blank video as Jez suggested at around 70p!
Other useful(ish) features on the Panny E30 include the TimeSlip where you can start recording a programme and before it is finished recording and you start playing it back... I'm sure most of us have wanted to start watching before we have finished recording on numerous occasions - I know I have! It's very easy to copy your TV recorded films up onto DVD too.
A variety of recording modes (similar to your VCR) are also available that record in different quality... it's a trade off between time recorded and the quality. eg 1 hour recording on a 4.7Gb DVD = perfect quality, 6 hour recording = lower quality. I haven't really used any of the really low quality modes yet (shouldnt thinki will) so can't comment to what they are like against VHS quality...
Downside is the cost of the machine (in comparison to a VCR anyways)... but they are falling very quickly with the fairly recent 'budget' pair from Panasonic (DMR-E30) & Philips (DVDR890)
Worth a look in my opinion for all of Joe Public...