Dual Layer DVD Burners are here
Tom's Hardware Guide Mass Storage: Lite-On, LG and BenQ Bring 8.5-GB Recordable DVDs to the Party - 16x: The Final Destination?. At last the DVD burner market is maturing.
The DVD+RW and DVD+R format seems to be the winner. Both can go to 9GB on a single side and to 16x (that's 10,000 rpm folks as fast as a hard drive).
The main issue is the media is expensive. Most important thing is to update the firmware. There is going to be a pretty long period of incompatibilities between media and drives so you need to read the forums to get the right drive and the right media.
They tested three drives and the Benq 1600A is the fastest particularly at burnding DVD+RWs, so that make the most sense if you are burning lots of DVDs (like me). If you want DVD-R and DVD-RW as well then get the LG GSA-4120B.