Just thought I'd throw my hat into the ring. The latest f/w for all three models (1640/1650/1655) has I believe a new algorithm for SolidBurn. This results in a learning curve that is more gradual than previous. Hence initial response is poor by comparison. Stick with it & it's probably a fair amount better. This doesn't ironically mean that I'm recommending you upgrade. This is because if SB is enabled for known media it's longer to learn (increases the number of 'wasted discs' during this process). Is more descriminating on fresh batches of the same media (even new tubs of the same batch). Is more sensitive to rogue discs throwing the learning process off track. Hence results do seem to lack the consitancy achieved with earlier f/w.These suggestions as to what's going on, are what appears to me to be happening. So speculation nothing more. To see if there's anymore substance in my suggestions, more time needed. So unless you like playing around with different f/w & media, it may pay to hold back. For now anyway.