PC User magazine in Australia just reviwed double-layer DVD burners and gave their top award to the LG GSA-4167B.
Here's what they had to say about the BenQ DW1650:
"Unlike many other burners from BenQ, the new DW1650 leaves out HP's LightScribe technology and therefore has a reasonable low price tag.
"Howere the odd thing from our tests on this drive was the comparatively poor (although still within spec) disc burn it produced. With over 161,000 PI errors and a PI error peak of 57, it didn't exactly kjnock us over with its burn quality. To its credit, it still managed to stay on the right side of the specs.
"In temrs of burn speed, the DW1650 was almost half a minute faster than the Sony internal drive (a rebaded DW1640), although it was still a minute slower than the LG GSA-4167B. In terms of nominal maximum burn speeds, the DW1650, like the LG, only supports DVD-R double-layer discs at 4x, compared with 8x for the leading drives, so that also drops it down just a fraction.
Its price tag makes this one of the cheaper drives on the market, but despite BenQ pushing its SolidBurn technology, the burn quality here was not the best. Even with excellent media, the burn quality didn't do enough for us to confidently use it for mastering or archiving."
Other people I've spoken to have been very impressed with the burn quality, and even find the output tends to have fewer problems being read on other devices.