This from in impartial and fairly inexperienced observer:
Ive spent the past 3 weeks reading all the 1640 posts I can find, and the 1620 posts they compare/link to.
the 1620 was perhaps the drive to have 2 or 3 months ago. It still would be a fine choice if you need a drive RIGHT NOW. The 1620 Pro Bonus kit (Includes 25 DVD+R and 25 CDR discs) is only 49 bucks delivered to CUS at NEWEGG. Cant argue with price, hell, thats a great price on a proven great RETAIL BOXED drive WITH a bunch of media!
BUT...
It does have ALOT of threads the past 6 months on I HAVE A DEAD 1620, MY 1620 QUIT SUDDENLY, MY 1620 NO LONGER BURNS/READS AT FULL SPEED...also, possibly related, the MY 1620 RUNS VERY HOT!!!
The primary difference in physical design of the 1640 to the 1620 is IMPROVED COOLING DESIGN. They probably did that for a reason(Who designs something that costs alot of money to re-engineer unless they stand to improve something?). So it may well be worth the wait (say 3 or 4 more weeks) if you arent in too big a rush.
The media scans I see on this forum mostly show the 1620 is usually BETTER than the recent scans of 1640 burns(Especially with certain media)...BUT, the 1640 is all of 30 days old. Its on its 3rd official firmware. If you searched back to last year when the 1620 was "new", its early firmware results were lower average quality than the current results people are posting with 1640s. What that says to ME is, the 1640 is still very immature, but is farther along than the 1620 was when IT was a month out of the gate. WIth BENQs solid history of frequent firmware updates and extensive improvements regularly...coupled with the 1640 already seeming to be a very solid choice ALREADY that makes GOOD burns on alot of media...the future SEEMS to be bright for that drive. My old toshiba 5272 is having issues with error correction nowadays. I know its over 2 years old now, its tired, burned hundreds of discs...aligment is probably a bit off now. I want to repalce it so I dont have to worry about having to throw coasters away at record numbers and MAINLY so I dont have to reinvest the TIME to reburn stuff that should be good the 1st try.
AFter reading must be 200 posts on 1640 and 1620 burns, probs, speed results, and media compatibility...(Not to mention the shameless taunting and flaunting of the euro and asia members who actually can GET 1640s already...remember, all of us in the US are PISSED at you! :bigsmile: Nyeh!) I am waiting for a 1640(That or a rebadge that is less than 75 bucks). My brother has a 1620pro, and its an attractive option...especially at current pricing...
But the 1640...is almost worldwide now. And the early results...say it may be the longterm solution for AT LEAST the next 12 hours...maybe longer depending on the next batch of uploads. 
