Updating firmware for the 7240s is not difficult, though there is always some risk when updating firmware. Unless you have a power outage while performing the flash, you should be ok.
I always burned DL discs at 4x. With single layer Verbatim, I usually burn at 8x or possibly 12x depending on the drive I'm using.
The 7240s was a good drive, but not an outstanding one in terms of writing quality. Most people around here with experience using this drive say it is not as good as the previous drives in this series, the Optiarc 7200s or 7201s. I found that the 7240s does not write particularly well to mediocre discs, like some Ritek F1 mid code discs. So I used TY and Verbatim in it, and kept the burning speed down to 8x on single layer discs.