Flashing with official firmware and flasher will not void your warranty. Unfortunately, to flash the OEM version GCAB to the Retail BCDB we need to use unofficial flasher, thus will void your warranty.
So far I havent had a bad burn with the GCAB firmware yet, but Nero CDSpeed can only scan DVDs at 0.3x, which makes me want to flash to BCBD again.
Yes, that's a typical issue when you try scanning with GCAB firmware. It will only scan at around 0.3x and the result is not comparable to other scans in this forum.
But I am not sure if my bad burns was due to firmware or physical hardware.
It might be also your media.
So I am still debating if I should flash it.
Different firmware will result differently. If we are comparing GCAB/BCAB and BCDB, the latest BCDB has fixed several issues and in particular see their release reason point 1.
Release Reason (BenQ DW1655 firmware BCDB)
1. Improved the writing quality by updated writing strategy.
2. Improved LightScribe printing quality.
3. Fixed QScan hang issue.