I recommend SONY 710UL but if you are a rich Guy 800UL might a good choice too.

My experience: I have a laptop with Dathon 1.5Gb 512M DDR 60GB. Because of low capacity of my HD, an external DVD burner is necessary. In the beginning I preferred buying BENQ ,however, I found the price of SONY 710UL was dropped very fast, so I change my mind to buy SONY since it's brand means quality. So far I have burned 30 discks without any failure. Fuji DVD -R 8x is the DVD I used, although others suggest using +R DVD. The result still good when I use -R DVD.

BTW The shape of SONY DVD burner is another reason I chose it. Dont forgot the style and outward appearance is much important when you buy "external" DVD burner.