While the BenQ is just as troubled by "getting a bad flash" as the LG products, there is one major difference: BenQ can recover completely from a bad flash just by flashing it again. So, in this event, you will not have to mail it.
Should you become slightly stuck with a "bad flash", firmware L9 (from www.benq.com support downloads) can clear things up very easily. If you get really stuck, the DOS flasher, using the 1620's retail firmware from the "unofficial" firmware page will fix it almost instantly (but it is rare to need this).
In fact, the only way to figure out that you may have a bad flash on a BenQ is to compare your quality scans (cd/dvd speed from www.cdspeed2000.com ) with our "post your scans" thread here at the forum. If you don't get a near match, just flash again. No problem.
I had two LG's and a bad flash (resulting in chronic "FOCUS" messages) meant sending the drive through the mail. Now I have two BenQ 1620's and a bad flash is so unnoticable that it is hard to detect as the drive still works just fine. Flashing again cures the problem completely.
That's why some people flash in safe mode. Although it is unnecessary because a flash problem is SO easy to detect and fix, safe mode loads windows without 3rd drivers or virus checker to interfere.
P.S. Scan some of your burned discs before you flash. Use cd/dvdspeed. Now, scan some discs after you flash. Firmware P9 (useful for "troubled" or old computers) will produce the same results as the earlier firmwares. Firmware T9 scans usually look slightly worse (very slightly) and the playback/data integrity has been improved.
Anyway, firmware upgrades are worry-free with the BenQ products.