The way I heard it the DVD+ drives are more compatible with DVD players. They're also less likely to produce coasters. There's a couple drives that do both plus and minus. You could get your Dell without a burner and add one of those.
I went for the Plextor 504 which is a DVD+ burner. I wanted to archive my laser disc collection to DVD's because the laser discs aren't very permanent. I haven't had time to try any movie burning though. To do DVD's it's fairly complicated, you have to decode the movie first, then shrink it to fit on a 4.7Gb disc.
Here's a good place to get info on doing DVD stuff: http://www.doom9.org/index.html?/right.html
DVD FAQ site: http://www.dvddemystified.com/dvdfaq.html#2.10
another great site for info: http://www.dvdrhelp.com/
