Why?
Let me count the ways: 

1. The five competing formats (DVD±R, DVD±RW, and DVD-RAM) each have a different blank disc with different prices, 

• Only DVD-R is likely to play on the existing DVD player hooked to your stereo and TV.
• DVD-RW will probably play
• DVD+R might play. 
• DVD+RW will probably not play on most DVD players. 
• DVD-RAM will usually only play in DVD-RAM drives. 
The DVD burner in your computer will ,of course, play every format it can create, but probably not play any other formats except DVD-ROMs and DVD-Rs. Making you crazy yet? And what about the DVD-ROM drive you already have in your computer? Forget about DVD-RAM which uses 4.7 GB single sided discs and 9.4 double sided cartridges that only work in DVD-RAM drives. The other two rewriteable formats (DVD-RW and DVD+RW) may or may-not work, you just have to try them. 
 
2. Prices of blank media and DVD drives are falling really fast right now, but pay close attention to the write speed of the media you buy. The folks that track these things, predict that within a year, DVD drives will be close to what they are getting for CD drives now, and many new DVD drives also have full CD-RW capability, although at a reduced speed. A DVD and CD burner is a Super-Combo drive. A CD-RW burner with a DVD-ROM is a Combo drive.
    
3. Microsoft has blessed DVD+RW as the rewriteable format it will support in future Windows releases, but business’ doing mostly data backup should go with DVD-RAM. A little slower, but with better error correction. They also claim you can rewrite the -RAM discs 100,000 times.
    
4. Disc termination times vary with every format. DVD+RW is supposed to have the shortest time. Rewriteable discs have to be formatted before burning. The DVD-RW takes over an hour to format (some third party software is faster). The DVD+RW takes a few minutes at the start and formats on the fly as you record, making it the fastest choice. 
    
5. DVD-R burner speeds are increasing. Last year, it was 1X (11 mega-bits per second). Most currently on the market are 2X with some third generation drives at 2.4X. The 4X standard has just been approved, so they should appear on some drives by Christmas. Drive makers are forecasting 6X next year with a more powerful diode. Most drives still burn rewriteable media at 1X. This is starting to increase to 2X and 2.4X.
    
6. New technology is coming on fast. Blu-ray (9 big drive makers) and the blue laser that Toshiba and NEC are working on should be in stores the first of next year. Multi-layer recording shouldn’t be far behind. Why is this important? Next year, if congress gives the entertainment industry everything they want, HDTV should take off. That 23 to 27 GB that Blu-ray will burn on one side of a disc (the same size as a CD), will handle about 2 hours of video. Unless Congress mandates the cop-chip. Then all bets are off, because it will be a whole new ballgame. We just might see the Right-Now generation show us old folks what civil-disobedience can really be like and the MP3 fiasco was just a warming-up exercise. I can see it now, “The only way you’ll take my burner is from my cold, dead hand”. But I digress!
   
   
7. ESS Technology that did such a swell job on protecting the DVD movies has now developed new encryption/decryption LSIs for DVD recorder/players for MPEG-4 and WMV (Windows Media Video). All they have to do is keep those Norwegian kids away from them

You can also look at the fluff tests on ZDNet and PCWorld. Remember, they are trying to sell stuff, not protect you from inferior technology. Latest prices are at Pricewatch.com and Pricegrabber.com or whatever shopping bot you prefer. Prices on these buggers change weekly and you won’t believe the price spread from the different shops for the same drive.

Don’t forget to look at the software bundle before you scratch that itch. Most have Sonic’s MYDVD. If you read the user comments, this dud has a long way to go before it reaches the level we expect from current CD burner software.

One last thought. If your computer rig is over two years old, plan on some big-time problems and upgrades if you add a DVD burner. Still have that adventurous spirit? Don’t say I didn’t warn you.