The current official latest firmware is BYX2. You can get it here. My drive came with firmware BYZ1 and I was reluctant to "upgrade" to BYX2 because it seemed like that would be going backwards, but I eventually gave in because with BYZ1 the drive had serious problems reading the DVD+R discs it burned. Switching to BYX2 fixed the problem.
You can also see a review of the BYX2 firmware here. The reviewer recommends installing it, and so do I.