Most DVD recorders do not have good tv guide functionality. They won't follow a show if it moves time slots. They will not ignore repeats. They fill up MUCH quicker, so if you watch more than a couple of shows a week, then you need more than one DVD recorder or to remember to switch discs.
That being said, I use dvd recorders and cancelled my satellite tv. The DVR wasn't worth the extra money to me. Instead of paying $700\year on that, I am building an HTPC (to replace the dvd recorders) for around ~400 that will record all my local shows, and I bought an HDTV decoder to receive all my local channels in high def. After year 1, I'll be saving money like a madman while still getting the programming I want most.