I use RW media frequently to transfer TV shows from my PC to my Divx-capable standalone DVD player. I only use DVD-R to archive a whole season and then only for shows I know I will want to view again in the future. So, the rewritable capability has uses for me.
I find that - no matter how careful I am - regular RW media gets scratched up and then doesn't work properly.
So, I find that by far the best RW media is Verbatim 4x DVD+RW "Videogard" media that are "over 40 times more scratch resistant".
Buy.com has them for $13.99 for a 10 pack (which comes in slim DVD cases) and also has free shipping on orders over $25. You can find other stores by searching froogle.google.com .
This is cost effective, because they should last longer and not need replacing as often as cheaper RW's.