There is one potential change in the 08 and 09 firmware. Due to further adjustments in the laser calibration, some media is now causing the drive to slow the burn speed late in the burn. The result is a longer burn time than if you had chosen a slower burn speed. This is a drive-specific issue, just as it is with the 6S drives, some drives will behave differently than others. TY media is affected, as are others. It's the cost of increasing laser power in order to lower read eror rates.
One interesting note is that the 7S drive can downshift the burn speed without pausing, a very nifty trick. If you're not watching the speed indicator in Nero, or listening to the drive, you'll never know it happened.
But anyway, earlier firmware will give you higher measured read-error rates with faster speed on more media, later firmware will give you lower error rates and less speed. With RW media, the later fimmware gives the best quality.