Been at work all day, just got home.
There are many DL writers that are of good quality. You can ask for opinions in the DVD Writer section of cdf. I use the BenQ 1655 (about $40.00 US) and am very pleased with it's flawless performance. Be sure the burner you buy will booktype +R DL media to the DVD-ROM Standard so you get consistant player compatibility.
But there is only one maker of quality, reliable DL media at this point in time. Buy Verbatim DL +R media.
As far as worth the cost ... yes and no. Since I play my backups on pretty hi-end equiptment, I never compress because I refuse to suffer loss of quality. The very special movies in my collection (Gladiator, The Lord Of The Rings series, Special Edition Boxed sets like the Alien Quadrilogy etc., etc.) get backed up on the somewhat more expensive DL media. Other movies get backed up by splitting the DL original onto two SL blanks. For single layer brands, I use Verbatim and Taiyo Yuden only. Ordered online in cake-boxes of 100 the cost including shipping is about .60 U.S. cents per disk or less sometimes if Verbs go on sale at a retail store (TY's are only available at Web outlets like Rima.com ... watch out for cheap "fake" TY's from some other sources). DL Verbs can be had on sale for about $1.85 U.S. per disk.
.60 x 2 = $1.20 to split a movie VS $1.85 to burn a movie to DL media.
Not too much difference depending on your income and the size of your collection of originals. But unfortunately, some countries don't enjoy the competative pricing of the US and I don't know were you live.