I got the Pioneer A03 (2x) and it seems quite good. The Pioneer A04 is recently released, so you should be able to get an A03 cheap (try compgeeks, I've seen it for ~$400). I haven't been watching the A04, so I don't know what the price will be.
Know your media types before buying a drive! There are a few "standards" going around such as DVD-R, DVD-RW, DVD+RW, DVD-RAM, and a couple others I think. DVD-R is akin to CD-R (burn once) and is the common denominator among all DVD burners I've seen. I chose the Pioneer drive becuase it also burns DVD-RW (which is like CD-RW and is the most compatible format I've seen other than DVD-R). DVD-RAM requires a caddy which is suck IMO.
Don't take my word for it! Do some research